Transcripts
1. Introduction: Hi, My name is Meredith. I'm a landscape photographer and outdoor educator based
in Denver, Colorado. In this course, I'll be
teaching you how to read and understand image histograms
in Adobe Photoshop. Histograms are essential tools
and digital photography, but they can be intimidating and confusing, especially
to beginners. That many people skip
over learning histograms, but this is a big mistake, especially if you want to
improve your photography. Here's some of the
most important tools that you can use to
improve the quality of your photos as they
allow you to evaluate the overall exposure and
color balance of your images. In this course,
you will learn how to read image histograms in a way that's simple
and easy to understand. We will start with the very
basics from what histograms, even our two, how to open them up and analyze
them in Photoshop. You will also learn about
the different types of histograms that you'll
most likely encounter, such as luminosity
and RGB histograms. And how to use them to
correct and improve the exposure of your images when you're editing
them in Photoshop. This course is for anyone
who wants to improve their photography using image editing and
post-processing tools. Beginners who are brand
new to the concept of histograms will gain a
lot from this course. And more advanced
photographers looking to master this topic will benefit
from this course as well. So if you are ready to
join me in learning how to nail the exposure in your
photos using histograms. Then I look forward to seeing you in the
very first lesson.
2. Understanding pixels and image sensors: Welcome to the class. You-all, I'm so excited
to have you here. In this first lesson, we're gonna be
discussing what pixels are and how pixels are
used and how they work. In the context of
digital photography, you might already be familiar
with what pixels are. And if so, that's great. This will mostly
be review for you. But this is a really
important concept for you to understand in
digital photography. And it's a concept
that really lays the foundation for
how histograms work. So what is a pixel? A pixel is the smallest unit of information in
a digital image. Now, what does that
actually mean? You're looking at here
is a photo that I took in Rocky Mountain National
Park in Colorado, which is a beautiful
national park in the Rocky Mountains near
where I live in Denver. I shoot a lot in this area. And this is a digital image in the raw file format that I have done no editing
or processing to. In order to understand
what a pixel is, let's zoom all the
way into this photo. I'm going to zoom in
all the way that I can possibly zoom in until I
can't zoom in anymore. You'll start to see all
of these little squares. If you're trying this out
at home on your computer and you're having a hard time seeing all of these
little squares. Which you can do is you
can come up here to View. Then down to show over to
this sub-menu to pixel grid. And you'll want
this to be checked. I usually don't have this
checked when I'm editing, but it's a great way to
see individual pixels. If we come back to our image, every single one of these
squares that you're looking at is a single pixel. And the word pixel is just an abbreviated word
for picture element. And each one of these pixels represents a single
point in the image. And each pixel has two
distinct qualities. The first is color, so each pixel has
a single color, and the second is brightness. So each pixel has its own
unique brightness level. And this is going
to be something that's important to remember, especially as you edit photos. So again, each pixel has
two distinct features. One is color and the
other is brightness. So each one of these
pixels is just a unit, a single unit of information. And when combined, if
we start to zoom out, you'll see how they
all come together. They combine into a
single photograph. As we zoom out, we get bigger and
bigger perspective. And these pixels
are so tiny that we can't see them when we
zoom all the way out. This photograph in
particular is composed of a little over
45 million pixels. One of the reasons I know
that is because my camera, which I shot the
photograph with, has a 45 megapixel sensor. And we'll discuss what that
means in just a moment. So where do pixels come from? How are they created
by the camera and transferred into this digital
image that you see here. Well, to understand that, let's talk about
how a camera works. In digital photography, a
camera captures an image by recording the amount of light that falls on the image sensor. And the image sensor, which is represented in this
illustration right here, is just a light-sensitive piece of hardware in your camera that captures light
from the scene and transfers it into
a digital image. So let's say we're out shooting a photograph of this mountain. When sunlight hits this scene, the sun could be
anywhere from this side, it could be behind this
mountain or it could be behind us when
we're shooting. All that matters is that
when light hits this scene, it's reflected off of this
scene and back towards you, the viewer of the scene. So wherever you are
with your camera, that reflected light is
going to pass through your camera lens directly from the scene as
it bounces off. And it's going to travel
through your lens and then into your camera at where
it hits the image sensor. And the image sensor just lies
directly behind the lens. So in this illustration, the lens has been removed. And if you were to be at
home looking at your camera, if you have, say a DSLR
or mirrorless camera, when you take off your lenses, you'll be able to see the
square image sensor in this opening where the back
of the lens attaches to. I don't recommend that you take your lens off your camera very often or frequently for an
extended amount of time, because it exposes the
image sensor to dust and other types of particles that can damage your image sensor. You definitely
never want to touch your image sensor and definitely protect it
from the elements. Don't let anything touch it. Again, the image sensor is
just a piece of hardware in your camera that collects light information
from the scene. And what will happen
when the sensor collects this light information. Your camera, through a
very technical process, will transfer this
light information into digital information, so it'll turn it into
the digital image. Another way to think about this image sensor is it's
kinda like how film, like 35-millimeter film, used to be in cameras
in the old days. Film is just a
light-sensitive medium that picks up light information. Your image sensor is doing the exact same thing just in a lot more sophisticated way. Now, let's take a look
at this illustration, which is a very, very simplified model of
an image sensor. Image sensors, just like your digital photo,
has individual pixels. So each one of these squares in this image sensor
represents a single pixel. If we were to count up
all of these pixels, the total amount of pixels
on this sensor is 63, so we have nine columns
and seven rows. So seven times nine is 63. In reality, modern image sensors have millions and
millions of pixels. Again, this is an extremely
simplified version, just to help you
grasp the concept of how image sensors work. Getting back to pixels, what each one of these
individual pixels does is it captures light and
color information coming from this scene
that you're photographing. And each one of these
pixels will translate into the pixels that
you'll ultimately end up with in your
digital image. So imagine each one of
these pixels is kind of like a bucket
collecting rainwater. But instead of a bucket
collecting rainwater, it's really just a collector or at theoretical bucket
collecting light. Each one of these pixels records a specific amount of
light and produces a corresponding digital
value that represents a specific color and
brightness of an image. Let's look at an example
of what that means. Here we have our 63
pixel image sensor, which we just looked at. Let's say we were shooting
a photo with a camera that had this 63
pixel image sensor. If you look over here,
the corresponding image. So if you use your imagination, imagine this is a photo that you took with that 63 pixel camera. The image could look
something like this. The colors could be a little bit different depending on
what you're shooting, but it would have
63 pixels in total. You can see here
too that 63 pixels gives you almost no
detail in a photo, which is why modern day cameras have image sensors with
millions and millions of pixels that so that you can get more pixels on an image sensor and get a higher resolution. So you can get much
greater detail in an image when you have a lot more pixels on
your image sensor. Again, this is an extremely
simplified illustration. Not just because of
how few pixels that are on this sensor in the image, but also because image sensors and the physics of
how they work and turn light into images are
much more complex than this, which I encourage you to read up on this stuff if
you're interested. And I'll provide some links
about image sensors and how this stuff works in the resources
section of this course. Now, in talking about pixels, you might be familiar
with the term megapixels, which is one of the
major specs of a camera that manufacturers usually
used to sell them. So usually higher
megapixel cameras are thought to be better, sharper, just generally
more desirable. With this term really refers to how many pixels the
image sensor contains. One megapixel is equal
to 1 million pixels. E.g. if you have a
20 megapixel camera, your image sensor has
20 million pixels, and it will produce an image
that has 20 million pixels. So if we look back at this
image of this mountain, we can look at the number
of pixels in this image by going to Image down
to Image Size. Right here, you can see that
the width of this image is 8,256 pixels and the
height is 5,504 pixels. If we were to multiply
the width times the height to get the total number of
pixels in this image, that total would be a little
over 45.4 million pixels, which is the exact same
thing as 45.4 megapixels. If you remember, one megapixel
equals 1 million pixels. You can try this out on
your own images at home. So for this, you'll want
to take a raw image, look up the width and
the height in pixels, multiply them by each
other and you'll get the total number of
pixels in your image. And that should
correspond to the number of megapixels at your
camera sensor has. So to review, a pixel is just
a single unit of an image. If we zoom all the way in, we start to see
individual pixels. In each one of these pixels
has a color and a brightness. Those two pieces of
information were collected by your
camera's image sensors. So the pixels on your
cameras image sensor. So that's a general
overview of pixels. Now that you have
that understanding, we can jump into what histograms are and how image
histograms work. So I will see you
in the next lesson.
3. How to read a histogram: Welcome back to
the class you-all. In this lesson, you're going
to learn what histograms are and how image
histograms work. I find that a lot of
people skip over what the histogram is when
learning photography. And I really think that
this is a big mistake. Histograms are an extremely
important aspect of digital photography that
will help you to properly expose your photos
both in the field and also when you're editing photos at home on your computer. Now, histograms do involve
just a tiny bit of math, but don't freak out if
you're not a math person. I'm going to break it down
into really simple terms. And I promised that by
the end of this lesson, you're going to have an
understanding of what histograms are before diving into what
an image histogram is. So the histogram right up here. Let's first talk about what
a histogram actually is. So histograms aren't
something that are completely limited to
digital photography. They're used in a lot of different ways outside
of photography. Let's look at this
illustration to help you understand what histograms are. Which you're looking
at right here is just a simple histogram. Histogram is just a
bar graph that's used to visually describe
information or data. Let's take a look at an
example of what that means. So right here on the
left is a bag that contains four different
colored marbles. We have red, blue, green, and yellow marbles. And as you can see, these different colored marbles, very indifferent amounts. We have three red marbles, five blue marbles,
one green marble, and two yellow marbles. What we can do using a
histogram is we can map out or graph the frequency that each color of marble
appears in this bag. If you look at the histogram, all we're doing here is counting the number of times a
specific marble occurs, and then plotting it using
this bar on this graph. At the bottom here,
on the x-axis, we have the different
colors or categories. Sometimes these are
also called bins, which is really just a
fancy term for category. On the y-axis here we have the number of times that
the marble appears. So if we look over here, we have three red marbles. So this bar reaches the
three on the y-axis. It's showing us that there
are three red marbles. The same thing follows
for the other colors. We have five blue marbles. So this part will extend all
the way up to number five, representing the frequency
or the number of times the blue marble
appears is five times. Same thing here for grain, we only have one, so it reaches up to
one on the y-axis. And same for yellow,
we have two, so it reaches up to
two on the y-axis. Now, we can use histograms
in any situation where we have a set of data that can be broken down into categories. And then each one
of these categories appear in a specific frequency. E.g. we could graph the
frequency of people's ages and a movie theater by
grouping people into categories that
represent different decades. So we could count the
number of people that were born in each discrete decade. So again, anytime we
can break up data into categories
and count how many times each individual
piece of data appears within that
category or the frequency, we can create a histogram. In the case of
digital photography, as we'll discuss here next, the frequency of pixels
in a digital image can be grouped by their
level of brightness or tone. Let's go back to our
tiny 63 pixel image, which we produce from our
63 pixel image sensor. This time our photo over
here is in black and white. So I've removed all of
the color information. And now all you can see
are the tones in the image or the levels of brightness from solid black to pure white. Now, just like in
the last example, if we were to graph
out the frequency of tones in this image, we get a histogram that
looks something like this. So if we broke these
pixel tones down into five separate
categories based on how dark or bright they are. We could divide them into
these five categories. Black, dark gray, 50% gray, light gray, and white. We could count over here how many pixels fell into
each one of these categories. And I've already done
this for you here. And you can see how many
pixels there are for each tone based on what
these bars are showing, we have eight black pixels, 19 dark gray pixels, 16, 50% gray pixels. 13 light gray pixels
and white pixels. Again, we are graphing the
frequency distribution. So the number of pixels for each one of these
tone categories. Now, in reality,
if you remember, the image that we've
been looking at has over 45 million pixels. The image histogram in Photoshop works the
exact same way. It takes all of the
brightness or tonal values of the image pixels and it maps
them onto this histogram. They're going to be millions
and millions of pixels graft onto the histogram. You can imagine that it's
going to be a little bit larger than what you're
seeing right here. So let's take a
look at that now. Back in our image. If we take a look at the
image histogram up here, if you see this little triangle with the exclamation mark, you can just click on it and it will refresh
the histogram. It just updates it. If you're not seeing your
histogram open in Photoshop, you need to do is go to Window, come down to histogram and
make sure that it's checked. In our previous example, we were looking at
an image histogram for image with five
different pixel tones. And in reality, the histogram that you're
looking at right here has 256 different tones graphed
on it, rather than five. When Photoshop reads this image, it assigns each pixel in that image a tonal value
or a brightness value. And it distributes them
along this histogram, just like we saw in
the previous example. But instead of just
mapping five tones, we're mapping 256 tones. If you were to zoom all the
way in on this histogram, you would see all of those 256 individual bars
making up this histogram. But because there's
so many bars packed in together in such
a small space, it looks like a smooth curve. To better visualize what's
going on in this histogram. Let's take a look at
this illustration. What you see here is
depicting exactly what you see on your
histogram in Photoshop, broken down into everything
that's going on. In this example, you can see
in a little bit more detail how the tones have been
graphed out from black. So zero being pure black, which in this
particular histogram, there are 0 bar at zero, which means there are zero
black pixels in this image. If we move all the
way to the right, we reach pure white. So the 255th bar would
represent pure white. Here again, we don't have any
pure white pixels because we don't have a bar right here representing any white pixels. Again, each one of
these bars is counting how many pixels in an image are at each one of these tones. If we were to pick out
a single tone here. So around middle gray, a little bit darker. This single red bar
represents the number of pixels a little bit
darker than 50% gray. Now, these ranges of
pixel tones can be broken up into five
different ranges. So here we have the blacks, which is the range of
the darkest tones. A little bit lighter is the shadows in the middle
or the medium light tones. We have the mid tones. Lighter tones are going
to be the highlights, and the lightest
tones are the whites. Let's go back to our image. Now. If we look at this histogram, we can see a spike in
the highlights and then a large amount
of pixels and a spike here in
the darker tones. Looking at this image, we can see that all of
this light area up here in the sky is probably what's causing this spike
in the lighter tone. So all of these are going to
be highlights and whites. We don't have too much
in the mid tones, just a little bit
in the mid tones. But the bottom part of this
photograph that takes up the majority of the
photograph are darker tones, shadows down in here, and really dark, dark
so blacks down in here. Now, one of the most
important things for you to understand
when you're learning histograms is how to correlate
what you're seeing in the image to the
histogram and vice versa, just like I showed you. And we'll be going
through more examples of how to do this in
future lessons. But I want you to start paying
attention in your photos. If you have a photo
open in Photoshop, pay attention to how the
lightest part of your photo corresponds to the
histogram and how the darkest parts correspond
to the histogram. Now one thing I want
to mention right here, you can see how this spike in the shadows and the blacks kind of gets cut off right here. If you see that in a histogram, don't worry because it doesn't necessarily mean there's
anything wrong with the photo. It just means that there
are so many pixels in this area that reach above the graph that we
can't even see them. So we can assume that this
bike could come off of the histogram and there are more pixels than can be
visibly graphed here. Since we're trying
to squeeze all of this pixel information
into such a small space. Sometimes you'll
see these spikes that jump off of the histogram. Now, if you want to
see the actual number of tones that are in each of these 256
tonal categories. You can come over here to
this little menu icon. Click on it, and then
click expanded view. Now you'll see an
option to select different channels and don't worry about all of
these channels. Now, I'm going to
click luminosity. We're going to talk about what these different channels
mean in a future lesson. Now, if you click
on the histogram, anywhere on the histogram, you can see the individual
bar that you're on. So the level is just on
a scale of zero to 255, you're at bar 213. And then you can
see the number of pixels that are at that tone. Again, this is more in
the highlight tones. There are over 682,000 pixels
just at that tone alone. Quite a lot of pixels at
that particular spot. And again, that's
probably somewhere up in here where those tones exist. So that is how histograms work
and image histograms work in Photoshop or whatever editing software that
you choose to use. At this point, you
might be wondering why any of this matters. Why is this important? And we're going to
start discussing that in the following lessons, where you're going
to learn how to use the histogram to dial
in proper exposure. In other ways that
histograms are great tools that can benefit
you as a photographer. So I will see you
in the next lesson.
4. Interpreting histogram shapes: Hey, welcome back to the class. In the last lesson, we
talked a little bit about how you can look at
an image histogram. And based on the
distribution of tones in that histogram and the frequency
of tones that you see. You can correlate that to what you're seeing in
your actual image. In this lesson,
we're going to dive a little bit deeper into this. We're going to cover some
really common histogram shapes and the types of images
that they correlate to. This is really going to help you start to be able to look at a histogram and immediately know what's going
on in your image. Let's now look at several
different types of photographs and how their
histograms correlate with the varying levels of tones and brightness
that we see in them. The image that you're
looking at right here is a very typical type of image
called a high key image. And what that means is
that it's a photo of a scene that is
mostly very bright and has a majority
of its tones and the highlights with
just a little bit of shadows and blacks. This photograph that
you're looking at, a tree on a foggy, cloudy day. As you can see, most of this photo is
lighter or brighter. So all of this guy here that
takes up most of the image, we can just tell by
looking at it that all of these pixels
are pretty bright. We would expect to see
a lot of bright pixels on the image histogram
from this photograph. If we look over here
at our histogram. And by the way, right
now for these examples, I have the channel on
luminosity and we'll talk about what that
means in later lessons. But what we're looking
at right here is the brightness of the pixels
in this image over here, we expected to see a lot of highlights and
brighter tones. And indeed, if we look
at the histogram, we can see that
most of the pixels are in the upper range
of this histogram, which means that the
histogram shows that there are a lot of bright
pixels in this image. Again, looking right here, we can see that I showed
you in the last lesson, this histogram is cropped. So there's a large
spike right here that extends off of this window. But this huge spike right here just means that we have a lot of pixels in this image that
are really bright and tone. So mostly in the highlights and also up to the whites
range of the histogram. Now, the tree on this image where we see the branches are, where the darker tones are, the shadows and also maybe a few tones in
the blacks range. If we look back
at our histogram, we can see that there are very few tones that are in the darker range
of the histogram. Remember that all the
way on the left side of the histogram is pure black. And all the way
on the right side of the histogram is pure white. So down in the
darker shadow areas, we have very few pixels, especially compared to up here. This shape of histogram is very typical of a high key image, which again is just
an image that has mostly highlights and whites and very few blacks and shadows. We also have very
few mid tones is indicated in the middle
range of the histogram. The most prominent feature
is this big spike. All of these bunched
up pixels up here in the upper region
of the histogram. Another way to think
about this is say you, I'd never seen the photo that this image histogram
was created off of. You could immediately
tell that this was a high key image just by
looking at this histogram. Let's look at another
example over here. This image taken in winter is mostly composed
of lighter tones. We can see the
brightest tones in the image here and
up in the sky and some less bright but
still pretty bright tones down in here and along here, and especially up in
the foreground here. This image isn't quite as high
key as the previous image. But if we look at the histogram, we can see a similar pattern. This time though, we have two spikes in the
brighter tones. We have one spike here, which correlates to the
brightest tones in the image. So back in our photograph, these tones up in here
and as well as the sky, these are the pixels
that correlate with these whites and
bright highlights up at the top of the histogram, really close to pure white but not touching the
edge of the histogram. So we know that there aren't any pure white pixels
in this image. We have another spike
here in the highlights, which indicates tones that
are still pretty bright, but a little bit darker than the tones in this spike here. So we can probably interpret
that this bike right here represents some of
the lesser bright tones. So some of the darker
highlights down in here and as well as
in the foreground. For the rest of the image, we see that there are very
few darks and shadows. And that is represented
in the histogram as well. We can see that most of
the tones that aren't highlights and whites are somewhere in the
mid tones range. We don't really have
any shadows or blacks. And we definitely
don't have any pixels that are pure black
because we don't have any pixels stacking up at the left edge of this histogram. Let's look at an
image that is pretty much the opposite of
a high key image. And that is a low
key image that is really exactly like a high
key image, but in reverse. Instead of having mostly
light tones in the image, we have mostly dark tones. So this is an image of the
moon at night and the sky is very dark and just the
moon is bright in this scene, as you might have already
started to expect based on your knowledge
of histograms so far, if we look over here, you can see a massive spike in the shadows area
of the histogram. And again, this one
spikes so high that it is cropped off
of this window. If we look on the right
side closer to pure white, we see a tiny little bit
of bright pixels up in the upper highlights
and whites region of tones that represents
the moon here. So we just have a small
portion of our photo, just a small percent
is the bright moon. And those are represented by these few pixels at the right
side of the histogram here. Again, if you were to
look at this histogram, you didn't know what the image was that it was taken from. You could immediately
tell that this pattern, which is a very typical
pattern of a low key image, you could immediately
tell that this image was mostly dark and had a little
bit of brightness in it. So again, this is a
very typical pattern you see in a histogram
for a low key image. Next, let's see a different
pattern of histogram. In this type of scene is
what you would call a high contrast scene or a
high contrast image. These types of images
are very common when you're shooting at
sunrise and sunset. Especially when you have
part of the sun in the sky. And you have a very
bright sky with perhaps the sun on the horizon
or somewhere in the sky. Then because the sun is so low in the sky because it's
at such a low angle, you get a lot of dark
shadows in the foreground. So in a high contrast image, we get a lot of
bright pixels and a lot of dark pixels
as you see down here. And looking at the
image histogram, we can see a
corresponding pattern. We see a lot of brighter pixels that take
up about half of the image. So this area up in here is
where brighter pixels exist. And we see that the other
half of the image is composed of mostly
shadows and blacks. We have a big spike over here, which corresponds to all
of these darker tones, all these darker
pixels down here. We can also see from
the histogram that we don't have a
ton of mid tones. We do have some up in
here and we can see that the pattern of brighter pixels is more of a bell curve shape, which really means
that there's more of an even distribution of tones
and the brighter regions rather than one
homogenous bright patch that would spike at a particular
point on the histogram. This is a more
gradual distribution and that kinda makes sense
when we look at this image, we see some really bright
pixels where the sun is, which corresponds
to these pixels all the way towards pure white. And it does look like
this histogram is actually touching the
right edge of the graph, which means that there are pure white pixels in the image. That can happen when
you're shooting into the sun because
the sun is so bright, sometimes those pixels
turn into pure white, and we'll talk
about that a little bit more in the
next few lessons. But we see around
the sun kind of a range of highlight tones. So even though they're
all pretty bright, we have some brighter highlights and some darker highlights. And down in here as well,
some darker highlights. So that's why we get more
of a gradual curve here. The darks, however,
this big spike means that all of these dark
tones, these shadows, are really within a
similar tonal range, which is why they all collect
together in this one spike. When you're looking
at a histogram for a high contrast image, you typically see this pattern. So you see a big spike or maybe even a more gradual
spike in the shadows, then the histogram will
dip down in the mid tones. So there'll be relatively
few mid tones in this area. And then you'll see another
jump again in the highlights. Sometimes you'll see
a much higher spike in the highlights here. But it's usually this
U-shaped curve with a spike, darker tones and a spike
in the brighter tones. Let's look at another
high contrast image. This image is quite
a different scene than the previous image. We still get a similar pattern. If you look over
at the histogram, we have a big spike in the darker tones with a
smaller spike here as well, but we are really missing a lot of mid tones in this area. Then we get another spike
up here in the highlights. Looking over here in the image, we can see how this
histogram correlates. We have a lot of highlights
up in this area, which looks like it could be about 20% or so of
the entire image. And if we look over here, we don't see a huge
spike in highlights. And that makes a lot of
sense because we don't have a ton of highlights in this image compared to how many pixels are in the overall image. Most of the tones in this
image, down in here, especially at least 50% of
the image are dark tones. And we see that represented
on this end of the histogram. We can see that a lot
of these tones are getting very close to black, and many of them are in
the blacks tonal range. Through here. Looking at the photo, we see a lot of really
dark tones down in here. And as well as down in here. These are some
extremely dark tones compared to appear where
we have very bright tones. So again, this would be
a high contrast image. Let's look at a
third example here. Again, this is a
very different scene than the last few scenes
that we looked at, but still a relatively
higher contrast image. So we have a region of brighter tones and a
region of darker tones. And we don't really
have a lot of mid tones in this image. If we look over here
at the histogram, we see a giant spike
in the shadows here, which presumably correlates to all of these shadows
down in here, as well as some of the
shadows up in the mountains. And then we have two spikes
and the highlights here, we have a brighter spike
closer to pure white. We have really bright white
or bright highlights. These will correlate to the
brightest part of this image. So right down in here is likely where that
spike is coming from, this bright region
right around in here. Then we have another
spike in the highlights. So a little bit darker tones
then these cones up here. And if we look at our image, we do see some
darker highlights. So up in the sky here, as well as some of the light reflecting on the sand dunes. You can see in the
image histogram, it looks a little
bit different than the other high contrast
histograms that we looked at in the
last few images. But it still follows the
same general pattern. We have a lot of darker tones on the left
side of the histogram. A U-shape where the
mid tones would be, then a region of
much brighter tones. So even though these are
broken up into two spikes, these together, I'll represent the brighter regions
of the image. So overall we have a
region of darker tones and brighter tones
with few mid tones. If we look at a low
contrast image, we get an opposite
shaped histogram. A low contrast image
mostly has mid-tones, so the majority of tones in the image lie within
the mid tones. And there are very little
tones, if any at all, in the darker areas and
in the brighter areas. And if you look at this image, you can see that there aren't any really, really bright areas. There are a little
bit over here, but not that much. There's not really a lot
of dark, dark tones. There are a little
bit over here, but again, not a
huge spike in tones. Most of the tones in this image, so mostly up in here and as
well as down in the sand, are in the mid tone areas. So they are about half
as bright as pure white and about 50%
brighter than pure black. And again, we can see
on this histogram, most of the tones lie within the mid-tone range
of the histogram with a huge spike up in here, with just a little bit
of shadow tones and maybe just a little bit of
highlight tones up in care. So if you see an image
histogram that looks like this, maybe like a bell
curve or it just a giant spike in the mid tones. You can infer that this
image histogram is of a photo that is a
low contrast photo. Another example here, this is just an image of the
texture of the sand. And this is really obviously
a low contrast photo. We really don't have
any dark areas and we don't really have
any light areas. And if we look at the histogram, that's exactly what we see. We don't see any lights, bright tones, and we
don't see any dark tones. Maybe just a few, but a huge spike here
in the upper mid tones. Because the brightness of
almost all of the pixels, most of the pixels
in this photo. Lie within this upper
mid tone range. So those are the
foremost typical shapes that you'll see on
an image histogram. So a high key, a low key, a high contrast and a
low contrast histogram. And understanding these
image histogram shapes will allow you to
more easily correlate what you're seeing
an image histogram to what's going on in terms of the distribution of tones and brightness
in your photograph. Now, you might be wondering
at this point if there is a right or a wrong
histogram shape. And the truth is
that there is really no right or wrong
shape of a histogram. The shape simply just
providing us with tonal and exposure
information about a photo. And it's just a tool that
we can use to calibrate the digital image
that we created with what we saw in the
field with our eyes. So our goal as photographers, at least most of the time
as landscape photographers, is to create images
that match what we see with our eyes when
we're looking at a scene. And we do this by adjusting exposure through the aperture, the shutter speed, and the ISO. When we're looking at a scene
of a landscape, say e.g. this scene right here. And we're looking at it in
the field with our eyes. We want to capture this
scene really as closely as we can to what we saw
with our actual eyes. And the histogram is a really great tool that you
can use as a photographer to determine how well
what you saw with your eyes matches the
photo that you took. E.g. if we're out shooting
this scene of this mountain, we know by looking at it
with our eyes that we have some really bright areas as well as some
really dark areas. We don't have any blacks in this scene when we're
looking at it with our eyes, we don't have any black pixels. So we don't have any true
black parts of this scene. And we don't have any true
white areas of this scene. We know that we have brighter tones and a
lot of darker tones. So I know by looking
at this histogram, these tones, the way that
these tones are distributed, really makes a lot of sons, and it really corresponds to
what I saw with my own eyes. If e.g. I. Shot this photo and I
weigh over-exposed it. And I'm just going to add an adjustment layer here
to just demo what I mean. And you don't have to understand how this layer
works at this point. We'll go over that more
in my editing courses. But let's say I overexposed the scene and it looked
something like this. When I uploaded this
photo to my computer, I got a histogram that
looks something like this. And as you can see right here, there are a lot of
pure white pixels which correspond
to the sky here, which is completely white. When I look at the histogram, I know that this wasn't
what I saw with my eyes. I didn't see any
pure white parts of the sky when I was looking at
this scene of the mountain. So I know that this
histogram does not accurately reflect what I
sought out in the field. This spike in the histogram where it's pure white
doesn't mean that the histogram is wrong or that there's anything wrong
with the histogram. It just means that I
overexpose the photo. So ultimately the shape of the histogram should
be used as a tool to evaluate the exposure and
tonality of an image, rather than as a strict
guideline for what is right or wrong in
terms of aesthetics. In the next lesson, we'll dive more
into this topic and how you can use the
histogram to determine the proper exposure
of your photos and to adjust exposure as well. And using histograms
to accurately judge exposure in addition to how well the scene that you
saw with your eyes matches the histogram
on your computer is really the essence of how we as photographers can use this
tool to our advantage. We will explore that
more in the next lesson. So I will see you there.
5. How to get perfect photo exposure using histograms: Hey there, welcome back. Now that you have a basic
understanding of how to read histograms and how to interpret different
histogram shapes, which you learned how to
do in the previous lesson. Now we can discuss
how you can use histograms to properly expose your photographs when
you're processing them in Photoshop or other
editing software. One of the most important
things a histogram can tell you about an
image is whether or not the image is underexposed or overexposed to the point that you've lost
detail in your image. So e.g. here's an image that we looked at in
the previous lesson. This is one of the higher contrast images
that we looked at. And if you look at the histogram
here, I'll refresh it. We discussed a little bit in the previous lesson
about how if you have pixels that touch either the right side
or the left side, it means that you have pure white pixels
on the right side. So if you have pixels that
touch the right edge here, you have pure white
pixels in your image. And if you have pixels
on the left edge or any pixels that touch the
left side of the histogram, you have pure black
pixels in your image. It's really important to
understand that if you have pixels that touched
the left or the right side, so pure black or
pure white pixels, it means that you've lost
detail in your image. And the reason this is
so important is that you have an image
that's overexposed. A histogram can tell
you if your image is overexposed if you have pixels touching the right side or underexposed if pixels are
touching the left side. And we'll look at
examples of under an overexposed versions of
this photo in just a moment, we can see that this
photo that we're looking at right now is
properly exposed, at least in my opinion. As a side note,
proper exposure is sometimes not necessarily
something that's set in stone. You, as the artist
has to determine what you deem to be
proper exposure. So in my opinion, this image is properly exposed
for the most part. The reason I justify that is because when I look
at the histogram, there are no pixels touching
the pure white end of the histogram and there's no pixels touching
the black end, which tells me that I haven't lost any detail in the image. It also means that what I saw with my eyes when I was
out shooting the scene in the field matches what I see here in the histogram because
what I saw in the field, I didn't see any pure
white areas of the image. I saw a bright areas
such as down over here. And I saw dark areas, but I didn't see any pure white or pure black when I was
looking at this scene. This histogram accurately
reflects that. Now let's say that I overexposed this photo
and I've just created an adjustment layer here to intentionally overexposed
this image in Photoshop. And now we can see that
this area in the sky, extremely bright, it's
actually pure white. And that is definitely not
what I saw in the field. So this image is not an accurate representation
of what I was shooting. If we look over here
at the histogram, you can see this bar up at the
250 tone in the histogram. So the pure white
tonal value that corresponds to all of the pure white pixels
that we see in the sky. You can also see down here, all of which should
be the shadows. So it should be the darker areas been pushed up into
the mid tones. And I know that when I
was out shooting that these areas were much
darker than mid tones. This histogram definitely
doesn't correspond to what I sought out in
the field with my eyes. The problem here, and
this is really key, is that when you have an
image with pure white tones, you can't recover
what was actually going on in that
area of your scene. You can't recover that
in post-processing. So no amount of adjustments and changes in editing
that you can do in Photoshop can bring back any of the detail in this area. If I over-exposed it when I was out
shooting in the field. Now, assuming that
this overexposure isn't an adjustment and that it's actually
the original photo that I shot in the field. There is no way that I can bring back the detail in the sky. I can darken down these
shadows so that they move from the mid tones
down back into the shadows. But this detail up in
where the pixels are pure white cannot be recovered. That detail is lost permanently. Whenever you see a
histogram like this, where you see a spike
in pure white pixels. A term that you can use
to describe this image or this histogram is
clipped or blown out. So we know that this
image has been clipped, or in other words, blown out because this
whole area is pure white. Sometimes in landscape
photography clipping can be okay. Say when you're shooting
directly into the sun, virtually anytime you're
shooting directly at the site, you'll have some pixels that
are blown out in your image. But in an image like this, where I want to retain
the detail in the sky. So where I really want
it to look like this, where there is a lot of
really beautiful clouds and light in the sky, I want to retain
that information. So clipping in this example would not be a desirable effect. Often as landscape
photographers, our goal is to capture as much detail as
possible in our photos. So clipping is usually not
a good thing and something that you're going to want to
avoid in most situations. Looking back at our overexposed
version of this photo, the only way that we could fix this clipping or this blown out image due to overexposure
would be in the field. That would be by
reducing our exposure, by changing one or more
of our exposure settings. So changing the aperture or
choosing a smaller f-stop, it could be by speeding
up the shutter speed, or it could even be by
decreasing the ISO. You can look at an
image histogram on your camera when you're
out in the field shooting. In this can let you
know if you are clipping the image
and overexposing it, but using image histograms
on your camera, even though they
work the same as the histograms we're
looking at here. That's a topic for
a different course, but definitely something that you want to learn how to do. You can look at your image
histogram in the field and see whether or not you're blowing
out pixels in your image, then you can adjust
the exposure properly. So when you get home and load your photos onto your computer and look at them in Photoshop. You don't end up with
photos that look like this, that are completely blown out and there's nothing you
can really do about it. Let's look at this photo, but this time underexposed. Again, this is just
an adjustment layer I've made to darken
down this photo. But imagine this is
the actual photo that I took in the field. This time in the
underexposed photo, we can see on the left
side of the histogram, all of these pixels here
are touching pure black, which means that this photo
has also been clipped. But instead of the light
tones being clipped, the dark tones
have been clipped. We have pure black in some of these areas
like down in here, maybe down in here as well. And that also is
typically something that you don't want to
happen in your images. Because when I was out in
the field shooting this, there were no pure black tones when I was looking at the scene. So this is an inaccurate
representation of what I was looking
at with my eyes. Just like when you have
lighter tones, better clipped. So pure white tones
in the image. Whenever you have
pure black tones, it means that you have
lost detail in your image, which like I mentioned before, is typically something
that you don't want. In addition, if we have pure black tones or clipped
tones in this photo, we cannot recover those details using post-processing
techniques. So there's no way
that I can bring back the detail in these
really dark areas. The only way I could fix this photo would be
to go back in time. Would be really nice when it and increase the exposure at when
I was shooting this photo. E.g. I. Could have
used a wider aperture, a slower shutter speed, or a higher ISO. Let's turn this
underexposure layer off. And to summarize the image, histogram is a really
important tool that can help you
determine whether or not you've clipped or blown out any of the tones are
pixels in your image. It can help you to
understand whether you have a proper image exposure. So e.g. this photo would be
properly exposed because the tonal ranges are in the proper areas that
I saw it with my eyes. We don't have any blown out or clipped pixels
touching pure white. And we don't have any
pixels touching pure black. This image histogram
tells me that I've retained all of the
detail in my photo, which is typically
an ideal thing to do when we're
shooting landscapes, it generally results in a more aesthetically
pleasing photograph. Now, if I wanted to
do any editing to this photo that I observe
as properly exposed, I could darken the
image down a bit. I could lighten it up a bit, but I wouldn't lose any detail. I have a lot more to
work with in terms of the data that I
captured out in the field. So that is a general overview of how to use image histograms to determine whether you have a proper overall
exposure in your image. We will continue to discuss
how image histograms can be a powerful tool that you can use to your advantage
as a photographer. And we will jump into that
more in the next few lessons. You'll also learn how to use different histogram channels. So looking up here, it will finally get into what
the luminosity histogram means and what some of these
other channels mean as well. And with that, I will see
you in the next lesson.
6. Using adjustment layers to balance the histogram: In the last lesson, you learned how to look at a histogram and
determine whether or not the exposure of your
image was sufficient. So whether or not the
image is overexposed or underexposed due to clipping that you see
in the histogram, looking for a pure white
or pure black pixels in the histogram. In this lesson, you're
going to learn how to take an image and adjust the exposure of that image
by changing the position or redistributing the location of where these pixels
are on the histogram. You're going to
learn how to do this by using adjustment layers. And this will all
start to make sense as we move through the lesson. There are three main ways
that you can manually adjust the exposure of an
image based on the histogram. The first way is to
use what's called a brightness contrast
adjustment layer. In order to find your adjustment layers or
to add an adjustment layer, you come over to this panel
where you see this circle. Click on it. And you'll see a variety
of adjustment icons. For the first one,
we'll click the sun. So this is the brightness
contrast adjustment layer. If we click on that, you'll see down here
that we've created a brightness contrast
adjustment layer. What this is doing is it's adjusting this layer
at the bottom. And you don't have to
understand at this point the details of how layers
and adjustments work. You can learn all about that in a Photoshop editing course. But for now, just understand
that we are adjusting the main image that is
at the bottom here. So the image that we're
looking at right here, if we look over here
at this window, this is where we can adjust the brightness and the
contrast of the image. I want you to pay
attention as we adjust these two sliders. What's going on in the
histogram up here. And I'll go ahead and refresh that first if we
adjust the brightness. So if we increase the brightness
to lighten up the image, you can see how the
histogram starts to press up against the
right side of the graph. So we're getting
all of these pixels blown out at pure white up here. So we know that we've adjusted
the brightness too far. If I bring this back down, you can see how the histogram starts to shift to the left. So we're darkening all of
the pixels in the image. So every single
one of the pixels in this image is getting darker. If we bring this
all the way down, we can make the image
really, really dark. And obviously that looks
completely unnatural. So we're not gonna do that, but this is just to give
you an idea of if you wanted to adjust the
brightness of your image, you can see how the
histogram starts to shift as all the pixels get darker and all the pixels get brighter. So I'm just going to put
this back at zero for now. Let's take a look at contrast. If we slide the contrast up, what you'll notice with the histogram is that
the highlights and the lightest tones get lighter and the darker tones get darker. If you remember from
earlier in this course, we talked about high
contrast images and how they typically have a
spike on the dark area of the histogram and a spike
in the lighter tones of the histogram with this you in the mid tones separating
those two spikes. As we increase the contrast, you'll notice that that
pattern starts to become more and more increased
or stronger and stronger. And eventually we start to clip some of these pixels
on the right side. Again, obviously this is
super unnatural looking. So I will bring that back down. The same if we pull it
down to the left here, you'll start to see the pixels move more towards the mid tones. So when these two spikes
come closer together, we're going to lose some of
the contrast in the image. And that's because the
darker tones are getting lighter and lighter tones are getting darker as they
move to the left. We'll pull that back up. So that is the brightness
contrast adjustment layer and how you can
use that to shift the tones in your histogram. Let's turn off this adjustment
layer by clicking here. And next, let's create
the second type of adjustment called a
levels adjustment. You come back up to
your adjustment panel. This time we're going to
click the second icon here. So this right here is
the Levels adjustment. Now we've created a
Levels Adjustment applied to our background
layer, our image. Here we can see all
of the controls and sliders for this
levels adjustment. You can see that this
histogram that shows up is essentially the same histogram that we're looking at up here. You only difference is this is an RGB histogram and this
is a luminosity histogram, which we'll talk about
what the differences between those two aren't
later in this course. But for now, just assume that
they work in similar ways. The levels adjustment tool
consists of three sliders, the black point right here, the white point on
the right side, and the gray point
in the middle. The black point
slider right here, adjust the darkest
areas in the image. So if we start to pull this
up and slide it to the right, what you're telling
Photoshop is that you want these pixels at the far end of the histogram
on the left here. You want those to be darker and you want them
to be pure black. If this slider
touches those pixels. You can see it as I slide
this slider to the right, it darkens down the darkest
pixels in the image. And notice appear at how the darker tones in the image
start to move to the left, they start to get even darker. Again. If I pull that down, the shadows are a
little lighter. And if I pull it to the right, we are setting the black point at the edge of the histogram. We're making the
darker tones darker. The white point works in a similar way, but
for the whites. If we pull the white
point to the left, what you're telling Photoshop
is that you want the brightest pixels in the
image to get brighter. So you want to have the
white point established at the point where
lighter tones used to be. And again, the
levels adjustment is a complicated tool and I
definitely recommend that you look into more in-depth
Photoshop editing courses to fully grasp
what's going on here. But the most important
point to keep in mind is that you are making the
lightest tones in the image, lighter by pulling
the white point down. And you're making
the darkest tones in the image darker by pulling
the black point up. The gray points
lighter right here, works in a similar way. As you pull it to the right, you start to darken
the lighter mid tones. And as you pull it to the left, you start to lighten
the darker midtones. It's a little bit
counterintuitive, but I encourage
you to play around with this and it'll
start to make sense. So what we're really doing
here is we're just shifting the tonal values of the mid
tones up and then down. Since this is a high
contrast image, we don't have a lot of
mid tones in this image. So if you look up here, there's a lot of pixels
missing in the mid tones. And for this image, sliding, the grade point isn't
really doing much, at least to my eye to
improve this image. For this image in particular, we definitely don't want to slide the white point
down because this is causing the pixels to blow out on the right side
of the histogram here. So Let's pull that
all the way back up. Sliding the black
point up just a little bit does actually
help this photograph. I think, by adding just a little bit more contrast by turning this
layer on and off. I do think that increasing
the black point, shifting the shadows
down a little bit does help out this image. The third type of
adjustment layer we can use is a curves adjustment. So that is the third icon here. If we click on this, what you can see here is another histogram representing
our histogram up here. The curves adjustment is
another tool that allows us to adjust the tonal
range of an image. And it's very similar to
the levels adjustment, but it provides more control
over the tonal range and allows for more
targeted adjustments of specific tonal values. And I'll show you
what that means here. Let's expand this window so that we can see this
entire window here. You'll see this diagonal line going across the
image histogram. Now, like I mentioned, this allows you to make
more targeted adjustments. And you do that by
clicking somewhere on this line where you want
to adjust the histogram. And then you can drag that line up to increase the
brightness of the tones, or you can drag it down to decrease the brightness
of the tones. Right here. When I'm
dragging this line, I'm focused on increasing these particular tones on
this part of the histogram. Let's say I wanted to increase the contrast of this image. To do that, I would
want to increase the tones on the right
side of the histogram. If we come over here
to the darker tones, I'll click on this level curve and drag this part
of the curve down. And you'll notice
wherever you click, you create a point and that will fix the curve at the point
where you click on it. And you can adjust where you
want these points to exist. You can create as many points along this
line as you want. So I could place a
point right here just by clicking on this line. And that will prevent
this area from shifting when I move
this area right here. So if I want to adjust
this line right here, I am going to have more
control of how light I make these lighter tones because I have placed a
point right here. The same thing over here
in the darker tones. I have more control. If I pull these down even more, they don't really affect
the lighter tones appear. Now, this is obviously way too much contrast
for this image. And you can see that
we've even blown out some of the pixels
on the right side. So I'm gonna pull this
down just a little bit and I'll pull up
the darks up as well. That does add a nice little bit of contrast to this image. If we toggle this adjustment
layer on and off, we can see how that
little pop of contrast adds a little nice
aesthetic to this image. Depending on your personal
editing preferences, you may or may not like more
contrast in your image. Let me increase the contrast. Once again, just to
demo real quick. We have a really
high contrast image here which does not look good. But just to point out this
S curve right here is a great technique
you can use when editing your photos and
you want to add contrast. This works a little
bit better on images that are more flat. So this is a pretty high
contrast image to begin with. But if you had a flatter image, you could create this S curve. And that's a really nice
way to add some contrast into your image by selecting
for the darker tones, as well as for the
lighter tones. You can see out we have way more control over the regions of different tones compared to our brightness
contrast adjustment. Where we didn't have
control over where we increased or
decreased the tones. All of the tones
in the image were adjusted by the same amount. I hope that helps you
understand how to use adjustment layers to shift
where the tones are in your histogram so that you can more easily match
what you saw in the field with your eyes to what the image histogram looks like
at home on your computer. And these adjustment layers, especially curves and levels, There's a lot more to
them and a lot more you can do with them when
you're editing your images. So I encourage you
again to go check out eight Photoshop
editing course. But for now those are the most important aspects of how to use those adjustment layers and
can really help you out when adjusting the exposure
of your images.
7. Luminosity histograms part 1: luminosity and brightness explained : Welcome back to
the class you-all. So far in this class, we've discussed the properties
of image histograms. And we've covered how they're
a graphical representation of the distribution of
brightness levels in an image. Now we're going to
break this down even further and you're going to
learn about different types of image histograms
that you will encounter when you're using Photoshop to edit your photos. If we look over here
back at our histogram, you will see these different
histogram channels. If you click here, you will see RGB, red, green, blue,
luminosity and colors. If you are not seeing
these channels right here, make sure that by clicking on
this menu icon right here, that you are in expanded view. This view will allow you to
see all of the channels. In this lesson, the type of histogram that
we're going to be looking at is called a
luminosity histogram. If we go back into
the channels here, the luminosity histogram
is right here. So I'm going to click on this. And if you're following
along at home in Photoshop, go ahead and also click on the luminosity histogram for whatever image you have open, we're going to dive into what
a luminosity histogram is. And luminosity histograms are really important for
you to understand. There'll be especially
important down the road when you start
to use things like Luminosity Mass when
you start getting into more advanced landscape
photography editing techniques. Alright, so if you remember, in the very first
lesson we talked about pixels and what pixels are
in digital photography. Let's zoom back in here so
that we can see our pixels. If you remember from
that first lesson, every pixel in an image has both a color and it
also has a brightness. One of the ways that we can
describe the brightness of a tone is through something
called luminosity. In photography, brightness
and luminosity are two different concepts that are often used interchangeably, but they have distinct meanings, so they are not exactly
the same thing. When talking about
the brightness of a pixel and the
luminosity of a pixel. Oftentimes you'll hear people use those words in the same way, but they are not
the same things. The brightness of a pixel and the luminosity are different, but they are a
little bit similar. So let's discuss what these two terms mean and
how they're different. First, let's talk
about brightness. Brightness refers to how we perceive the intensity
of light that hits our eyes after it
reflects off of an object or is emitted
from a light source. So in other words,
brightness describes the perceived intensity of light in an image or part of an image. If I zoom out here. When we're looking at this image and we're talking
about brightness. In this image, our eyes
perceive this area of the image to be much brighter than this
part of the image, which is the darker
area of the image. So the brightness up
in the sky is much greater than the brightness
down in the shadows. This seems pretty
intuitive and obvious that this area is brighter than
this area in the shadows. But since brightness is how our eyes perceive the
intensity of light, brightness can change depending
on our environment and the light source that's illuminating the scene
that we're looking at. A good way to think
about this is e.g. the brightness of your
cell phone screen. Let's say you set the brightness of your cell phone screen to about 50% and you walk
into a dark room. The screen at this
specific brightness will appear much
brighter indoors in this dark room than it
would if you were to walk outside and look at your screen outdoors on
a bright and sunny day. Even though you haven't changed the brightness level
on your phone, when you're looking at
your phone outside, usually have to increase
the brightness, often to up to 100%, just so that you can see
your screen on a sunny day. That's just because our
eyes have perceived the intensity of light
or the brightness differently outdoors
than we do indoors when it's dark and it's easy to see the screen at a
lower brightness. The way our eyes perceive
the intensity of light or the brightness can change depending on the light in
your surrounding environment. Alright, so luminosity,
on the other hand, which by the way, luminosity
is also called lightness. So if you hear the terms
luminosity and lightness, they really mean the
exact same thing. Luminosity is how we perceive brightness without
color information. Relative to 100% pure white. I know that probably sounds very complicated and technical. So let's break this down
into more simple terms. If we were to remove all of the color information
from this image, all of the pixels in this
image with lies somewhere on a scale from pure black
all the way to pure white. So if we were to remove all
of the color from this image, what we'd be left with
is the luminosity. We can actually do that to
this image in Photoshop. If you come up here to Image, down to Mode and
over to gray scale. Now we've removed the
color from this image. And if we zoom all the way in, you can see that all of the
pixels are gray in color. So all of these pixels
lies somewhere on a scale from pure
black to pure white, where 0% luminosity
is pure black and 100% luminosity or
lightness is pure white. Let's take a look at
this illustration just to help you
understand luminosity. When we remove the
color from the image, all of the pixels in the
image will lie somewhere on this luminosity scale
or tonal scale. At the far end here on the left, pure black would
be 0% luminosity, and pure white would
be 100% luminosity. Whenever we're talking
about the luminosity of pixels or the
luminosity of an image. We're comparing the pixels or the tones to pure white. So e.g. if we look at the
mid tones here, are 50% or around 50%, as bright as pure white. So whenever we're talking about
the luminosity of a tone, we're determining where
it lies on this scale. How bright is it
compared to pure white? In the highlights, we are about 75% as bright as pure white. Maybe somewhere 7080-85%
as bright as pure white. The white tones up here will be somewhere in the range of 85, 90% to 99% as bright
as pure white. And the darker tones down here, it will be about, around 25% as bright
as pure white. And the blacks, somewhere
in the range of five to 10% as bright
as pure white. These are just ranges
and not exact numbers. So looking back
at our image that has been converted
to black and white, Let's zoom out here. All of the tones
in this image lies somewhere on that scale
we just looked at. There's somewhere between
0% as bright as pure white and 100% as
bright as pure white. And we know by looking at
the histogram up here, if I refresh this, that we have no pure white or pure black pixels
in this image, because we have no
pixels stacking up on the right side at pure white and we have no
pixels stacking up on the left side at pure black. Let's bring the color
back to this image. And I'm going to zoom in
again to the pixel level. Now, the best way to look at
the actual brightness and the luminosity of each one of these pixels is to use the
color picker in Photoshop. The way to access your color
picker is to come over here. Click on this square here. And here we have
our color picker. Now, when you move
through the image, you will see this
eyedropper tool and you can click on
an individual pixel. So if I click on this
pixel right here, the color that we just
picked will appear here. And now we have some
really important values that tell us everything
about the color, the brightness,
and the luminosity of that particular pixel. So the particular pixel
that I just clicked on, the brightness, which is
represented by b, is 32%. So our eyes perceive
the intensity of the light coming from
that pixel as 32%. The luminosity or the
lightness is right here, represented by the L. The lightness or the luminosity
of that pixel is 34, which means that that pixel is 34% as bright as pure white. If we were to go
over and look at our gray scale over here, that pixel would lie
somewhere around here at 34% as bright as pure white. So that pixel will
lie somewhere in the shadows on the
luminosity scale. You can see that the brightness and the luminosity art similar, but they're not the
exact same numbers. And that's because they are
not the exact same thing. Let's pick one of these
brighter colors down here. And now you can see that both the brightness and the
luminosity has gone up. Now the brightness is 57%
and the lightness is 50. Again, luminosity would be
50% as bright as pure white. That is literally right down
the middle here at 50% gray. Remember that this luminosity doesn't have anything
to do with the color. It's just how our eyes perceive the brightness compared
to pure white. Let's close this up and
look at another example. We zoom out here and we look at the brighter tones in the image. Let's open our color
picker back up. Now I'm going to
click on the sky. Here we can see that
the luminosity is 95%, so it's extremely
close to pure white. It's 95% as bright
as pure white. But it is not pure white even though it might look
like it is to our eyes. And that's a good thing to know because we know that we haven't blown out our image because these pixels aren't pure white. So again, these pixels appear, these really bright pixels
with a luminosity of 95. We jump over to our
luminosity scale. They will lie
somewhere up in here, so they are extremely
light but not pure white. Alright, let's try one of
the shadows down here. We can see the luminosity is 24. So that is about right in
the middle of the shadows. We look back at our scale. 24% will be about right here.
8. Luminosity histograms part 2: luminosity and color: I want to show you
this illustration, I think will help the concept of luminosity sink in for you. Right here on the left
side of this illustration, we have the typical color wheel. So all of these colors right
here on the color wheel are fully saturated colors
at their full intensity. So this is what we call
hues on the color wheel. If you are unfamiliar
with the term humans, or saturated means,
which are just terms that refer to the basic
qualities of color. I definitely recommend that
you take some time to read up on or take a class
on color theory, just to learn some of the
basic concepts of color theory as this will not only help you understand
this stuff better, but it will also help you to become a better photographer. So I'll provide some links
in the course resources on color theory so that
you can read up on and study some of
this color theory stuff. If the concept of
saturation, hue, brightness, things like that are really foreign to
you at this point. Back to our color wheel. So we have all of these
hues on the color wheel. What I want you to
understand about all of these colors is that they all
have the same brightness. But our eyes perceive this
brightness differently. If I open my color picker here and I click on all
of these colors, you can see that the Brightness, the brightness of pure red
on this wheel is 100%. If I go around the wheel here, clicking the different colors, if you pay attention, the brightness of all of
these colors is 100%. You'll notice though that
the lightness or the luminosity changes when I click on these different colors. So even though the
brightness of all of these colors is the same, the luminosity is different. If you look over
at the right here, we have the exact
same color wheel. But in the middle of this wheel, the hues of the color wheel have been converted to grayscale. So they retained their
luminosity values. They are the same
perceived brightness when compared to 100% white. Around the color wheel here, I've shown what
percent of pure white that our eyes perceive
these colors to be. So in other words,
what the luminosity of these colors are. You'll see here red, e.g. red is 54% as bright
as pure white. If we convert red to the gray scale, retain
the luminosity. So we keep this gray
tone 54% as pure white. This gray tone is
how our eyes are actually perceiving this color. You can see here
that even though all of these colors have
the same brightness, our eyes perceive certain colors to be darker than others. E.g. if we look at Blue, Blue has a luminosity of 30, so it's 30% as bright
as pure white. And yellow is 98% as
bright as pure white. The luminosity is 98, so our eyes perceive
blue to be much darker in tone than
it perceives yellow. Our eyes perceive
the yellow to be very close to pure white. We can check all of this here. If we pull out our
color picker again, if we click on read, you'll see the
brightness is 100%, but the luminosity
or lightness is 54, 54% as bright as pure white. Looking at our gray scale
like we've looked at before, that tone will lie
somewhere around here. So a little bit
more than 50% gray. If I click on this gray
slice of the color wheel, which is just read with all of the color
information removed, you can see that the
lightness is still 50 for the brightness has gone
all the way down to 50. But our eyes still perceive the brightness at 54% as
bright as pure white. If I click on blue or blue converted to the gray scale
with the same luminosity. You can see that
this dark gray tone is 30% as bright as pure white. But that's still the
same luminosity. If we were to click
on the actual color, the luminosity
values are the same. So again, even though
the brightness changes, the luminosity, the way our eyes perceive the brightness
stays the same. Again, with yellow,
the brightest tone. It's at 98% as bright
as pure white. If I click on this part
of the color wheel, we see the luminosity is 98. And I will provide a link to download this illustration in the course resources so that you can open this
up on Photoshop, pull up the color picker, and test this out for yourself. Pick different colors and see where they lie on the
luminosity scale. So orange, e.g. 68% as bright as
pure white, orange. If we took all the
color information out, converted it to the gray scale, it would lie somewhere
around right here. So somewhere in
probably the highlights or upper mid tones range. The most important thing for you to understand here though, if you take anything
away from this lesson, is that luminosity is the
perception of brightness without color information on
a scale from black to white. Let's go ahead and close this up and come back to our image. Okay, so now hopefully
you're starting to have an understanding of
what luminosity is. So let's talk a
little bit about what a luminosity histogram is. We come back to our histogram
and I'm going to reset this on the luminosity histogram
and refresh that. Just like you've been learning
throughout this course, how histograms work by mapping the frequency of the different
pixels in the image. What this luminosity
histogram is showing is it's reading the luminosity of each one of the
pixels in this image, and it's plotting
them on this graph. Photoshop is reading every single luminosity
value for every pixel. It's determining on a scale from black all the way on
the left side to white, pure white all the
way on the right side where that pixel will
lie on the histogram. So e.g. if we take the color picker and
we look at our sky, so the luminosity of our sky, many of the pixels in the
sky here are around 94, 95, quite bright, really
in the 90s range. And that's why we see
this spike up in here. We see a lot of pixels with a luminosity value
higher than '90s. These are about 95% as
bright as pure white. Then we have the highlights. So really down in
the sand dunes here. So these tones in here
are about 50 to 70%. Some of the brighter ones
in here around 55, 56. If we look up in here, we also have more
highlight tones. So these tones in here
are around 83, 86. So in the '80s, these values have been here. In the '80s, will
correlate to this spike up here because
this is about 75, 80% as bright as pure white on the scale
from black to white. Then we have this huge spike in luminosity values and the
shadows down in here. If we use our color picker, luminosity of 2025, 18, it's really in the 15 to 25%, as bright as pure white range, luminosity of 15 to 25, which corresponds
exactly to the pixels that bunch up in this
area of the histogram. Again, this histogram is
just graphing the frequency of how many pixels exist
at each luminosity value. On a scale of black, 0% luminosity to white,
100% luminosity. Now what I want you
to do is open up a photo in Photoshop if
you haven't already, and open up the color picker, and I'd like you to just
move around your photo, guessing what the
luminosity of each pixel or area of the photo is and
seeing if you're correct. So see if you can guess
things like the luminosity of the shadows and the
luminosity of the highlights. And check right here at the
luminosity value to see if the luminosity
you guessed or the lightness you've
guessed is correct. This type of practice
will really help you start to read the
tones in the image. They'll help you to
understand how our eyes perceive the brightness of
the pixels in an image. So take some time
to practice this. Next, we're going
to move on from luminosity histograms
and we're going to discuss RGB histogram. So I will see you
in the next lesson.
9. RGB histograms part 1: the primary colors of light: Hey, welcome back to the class. In the last lesson, we did a deep dive into what
luminosity histograms are. Luminosity histograms are
really important to understand before we move on to what
are called RGB histograms. If you feel a little
fuzzy or unclear, or if you haven't
watched those lessons on luminosity histograms in the previous part
of this course, I definitely recommend that
you go and look at that now before you watch the
RGB histogram lesson. Because the previous
lessons that you saw are really going
to lay the foundation for the concepts we're going to talk about in this lesson. In this lesson,
we're going to focus on the RGB histogram. And if you look up here
to our histogram window, you can see that one of the
channel options is RGB, and that's what I have
it set to right here. We went over Luminosity
histograms and RGB histograms work in a similar way to the luminosity histograms
that we've been looking at. But they're slightly
different and perhaps a little
bit more confusing, especially when you start
to learn about them. So stick with me. We're going to break
all this down. And by the end of this course, you're going to
start to understand what an RGB histogram is, as well as what all of these other color
channel histograms are. So red, green, and blue. Rgb stands for, is just
red, green and blue. Rgb histogram, as we'll discuss, is a combination of a red, green, and blue
channel histogram. One thing that's
important to know about RGB histograms is that these are the types of histograms that are
gonna be on your camera. So if you look at the back of your camera after
taking a photo, or if you pull it up on your
live view, on your camera. If your camera has live view, if you pull up the histogram
while you're shooting, that histogram is going
to be an RGB histogram. Your camera might even give you the option to see
the red, green, and blue histograms
independently in that religious
depends on your camera, but most cameras at least
have the RGB histogram. So you won't see the luminosity
histogram on your camera, at least at the time
of this filming? There are no cameras that
I personally know of that have a luminosity histogram
or the option to C1. You also won't see a luminosity
histogram in light room. So if you're using Lightroom
to edit your photos, the histogram you'll
see in Lightroom is going to be the RGB histogram. And that's one of
the main reasons I've discussed in other classes. The main reason that I use
Photoshop to edit my photos because the luminosity
histogram is so important. But the RGB histogram
is important as well. So we'll talk about
what that is. Like I mentioned, RGB stands
for red, green and blue. And red, green and blue are
the three primary colors. When we're talking about light, when we're talking
about digital screens, like what you're
looking at here, say on your computer
or on your cell phone. Every pixel on your computer
or any LCD screen that you look at is composed of a
combination of only red, green, and blue light. When you look at an RGB
histogram over here, the RGB histogram shows
how many pixels in the image have a particular
combination of red, green, and blue values. So it's giving us information
about how red, green, and blue is combined
in the image to create all of the
colors that we see. Now, when you
combine red, green, and blue at their
full intensity, so at their full brightness, you get pure white. On this canvas here, half of it is pure white. So what that means is
that each pixel in this white area that
you're seeing on the screen is composed of red, green, and blue at
their full intensities. In contrast to that, the black pixels on your screen are a
combination of red, green, and blue pixels at
their lowest intensity, so they are completely
turned off. You could say. Let's take a little
closer look at what that means by opening up
our color picker. And let's click on the color
white to sample white. And if you look on
your color picker, right in this area, you will see are for red, g for green, and B for blue. What you see to the right is a level of intensity that
these colors are at, at that specific pixel
that we just sampled. Now, the intensity of each
color is on a scale 0-255. So there are 256 total
different intensity values. If you remember from
earlier in this course, we talked about how histograms that you'll be
using in Photoshop. Graph tones or brightness
on a scale from zero all the way on
the left edge here. So zero being pure black
and 255 being pure white. So that's what
this is over here. On the RGB values. It's showing where on a
scale of zero to 255, the intensity of
that color lives. You can see here that all of these three colors in the white pixel that
we sampled are. Full intensity. In other words, they're turned
completely on and you'll see them all the way on the
right side of the graph, which represents the full
intensity of the colors. And this will start
to make a lot more sense in a moment when we start to break down
these colors individually. But first, let's take
a look at black. Let's sample a
black pixel and you see how the values have
all gone down to zero. That's because each one
of these colors, red, green, and blue, are
now at zero intensity. They are all at pure black. Let's now look at each one of
these colors individually. Let's turn red all the way on. So if I type 255, I have turned red on
at its full intensity, as you can see in the color
I've created right here. You can also see
that green is at zero and blue is
at zero as well. This means is that we
have a pure hue of red at its full brightness
or intensity level. Once you start mixing
in any green or blue, this will no longer be pure red. So if I added in a
little green here, you can see how
that color changes. Let's try this out for green. So if I change this to
zero and green to 255, so we've turned
it all the way up to its maximum intensity. We get a pure green hue. And we can check that
as well right here. The hue is set at 120 degrees. So this right here
is the color wheel. And pure green is always at 120 degrees on the color wheel. Again, if color theory is a
little unfamiliar to you, definitely go read into
and study up on how basic colors work and
how we get pure hues. Let's try this out for blue. So I'll set this back to
zero and set this to 255. So let's full brightness
and intensity. Now we have pure blue, which you can see here. We can also check because pure
blue is also 240 degrees. It's always 240 degrees
on the color wheel. If you want to decrease
the brightness or the intensity of one
of these colors, you do that by adding
black to the color. So if we take our pure blue, which is fully saturated, we start to add in black
by dragging this down. If you watch the value for blue, It's going to start to go down. As you bring this all
the way down to zero, you can see that pure black
is represented by zero. If we look over here
on the color picker, what we're just looking at
is on a scale from zero, so right down here at black to 255 at the full intensity
of the color up here, our value for blue will lie
somewhere along this scale. So if we wanted to choose a value of blue
that was somewhere between black and 100%
intensity of blue. We could type in
something like 120, which is about half of 255. And you can see how this circle has moved halfway up the scale. It's important to
understand what these values mean right here and how they lie along the scale from black to full intensity. Because these are
the values that are going to be graphed
on our histogram. When we look at
the RGB histogram, Let's break down how this works. I'm going to refresh
the histogram here. I'm also going to
sample white again. So this histogram over here is an RGB histogram of this image, this black and white image that you're looking
at in the background. And you'll see on the
RGB histogram that we have a spike
appear in pixels, and we have a smaller spike on the left edge
of the histogram. So this is pure black and
this is full color intensity. When we're looking
at this image, we can see that about half of
the pixels are pure white. And again, that means
that red, green, and blue are turned
on at full intensity. This spike all the way
at the top here is representing all of the
pixels that are pure white. And it's graphing how
many pixels are at that 100% color intensity. So they're fully turned on. Now, this spike on
the left side here, if we sampled black, it's doing the exact same thing, but it's showing all
of the pixels in the image that have no
red, green, or blue. So those colors are
completely turned off. So again, this spike here on the left side is just showing all of the pixels that
do not have any red, green, or blue in them. Now, the caveat to the RGB histogram is
that even though it's graphing all three
different colors and their intensities
separately, and it's averaging
them on this graph. The caveat is that each of these colors are
weighted differently. And that's because
our eyes perceive green to be a slightly
lighter color. So Photoshop ways green twice. So it takes one red, two greens, and one blue and then averages those channels of light
rather than just one red, one green, and one blue. And again, that's
just because our eyes perceive green to
be a lighter color. This can definitely be
a little bit confusing. And I don't think it's
necessary to really understand the physics of how this works unless it's something that
you're interested in, then by all means, go and explore and
learn about how RGB histograms work by averaging the color channels differently. But it is important to
have a general idea of how these RGB
histograms work, as we'll discuss towards
the end of this lesson, how it can help you
as a photographer. Looking back at
our color picker, one thing I wanna show
you is how you can mix different channels of light
to make secondary colors. So before we looked at each channel or
color individually, Let's see what happens
if we were to add separate colors together
at their full intensities. So let's add red at its
full intensity at 02:55. And let's add green at
its full intensity. So it's combining red and green at their full intensities. What you'll see here
is that when you combine pure red and pure green, you get pure yellow. We can do the same thing
by combining other colors. So if I set this back to zero, keep Green at full intensity, and let's turn blue
all the way on. We get the color cyan. And if we turn green off and turn red all the way
up, we get magenta. And yellow, cyan and magenta are the secondary colors that we can create by combining the red, green, and blue primary colors.
10. RGB histograms part 2: reading RGB histograms and color channels: Alright, so now let's check out a Canvas that is pure red. And I think this is
going to help you more to visualize what's going on in these
RGB histograms. Let me turn this
background layer off and I will select
this red layer, and let's click
refresh the histogram. So now instead of
looking at white, which all of the colors were
at their full intensity, and black were all the colors. We're at zero intensity. Now we're looking at
a single pure color. We're looking at pure red. Let's take a look at what
the histogram looks like. The RGB histogram for pure red. So we get a spike on
the right side here and a much larger spike
on the left side. The spike on the
right represents red. And again, this is read at its fullest or
brightest intensity. The spike on the left that's touching the left
edge of the graph represents the green and blue
channels at 0% intensity. So they're completely black, or you could say turned off. And you'll notice the spike on the right is smaller than
the spike on the left. And that's because this bike represents one color channels. So just read. And this bike represents
two color channels, so green and blue. Now, unlike the
luminosity histogram, which is a histogram that
graphs the lightness values on a scale 0-100% lightness. This histogram is looking at three different colors and graphing them individually based on how intense they
are from pure black to the full color without
any black added to it. If we look here at our luminosity histogram
for this red canvas, you can see we have a
single spike in pixels. That's because the pixels
on this canvas all have a single lightness
or a luminosity value. We get out our color picker
and sample this color. You can see anywhere you click, the luminosity value
stays the same. So that's why we get
one single spike, because all of these pixels have identical lightness
or luminosity. If we switch this over to RGB. Now this histogram is showing
the different colors and the intensity of the three
different primary colors. So red, which is at 02:55, it's at its full intensity. We get those pixels stacked all the way
up at the right edge. And then green and blue, which are fully turned off, they're fully at Black. Those pixels representing
blue and green are going to stack up at the black
edge of the histogram. In addition to looking
at the RGB histogram, you can also look at each
individual channels separately. So let's first look
at the red channel, which just pulls out
that single color. Rather than having
it averaged out with the other two colors
in the RGB histogram. So if we select the red channel, we can see one single spike now. And that's because
this histogram is ignoring the green
and the blue colors. All this is saying is that
every single pixel in this image is at level
255 and intensity, they're fully turned on. Now, up to this point,
we've been looking at the three primary
colors that have been turned all the way on. Let's see what happens
if we add some red. But at a lower intensity value. If we take our color picker, we can drag it down
to add some black, say maybe about halfway down. We get read at about 120. Now we have a darker
shade of red. It's still the exact
same hue of red. It's still pure red since we can see red is at zero
degrees, right? Is always at zero degrees
on the color wheel. So we know we have
pure red still. We've just added some
black into the red. So we've lowered the
intensity of pure red. If I exit out of this and
select the brush tool, I'm just going to brush in
some of that darker red color. So if I brush this in here, we come up here and
refresh this histogram. Now you can see that
there are two spikes. The one all the way at the right side, like
we'd been looking at, represents all of this red
that is at its full intensity. Then we have a darker red or red that has
black added to it. We see that at about the
middle of the histogram here, we open our color picker backup. You can see how this color
of red is about 50% of the way down on the scale
from black to full intensity. And this spike right here
is doing the same thing. It's just showing that
we have red pixels in our image that are
about 50% intensity. We could drag this
down even more, create a darker shade of red. If I paint this onto the canvas. And we'll refresh this here, you can see we have a
third spike that is representing the darker
red in this image. It is getting closer and
closer to pure black. Or in other words,
the red is turning off as we add more
and more black. Now, if we go back to
the RGB histogram, we have three different
red spikes are the same ones that
we just looked at in the pure red color channel. Then we're getting
the information about the blue and the green channels, the blue and the green colors. Let's try out this
experiment with blue. If I turn this off and we
pull up our pure blue Canvas, I will refresh this
histogram here. We also need to
select that layer. Alright? This histogram
looks identical to the first RGB histogram
that we looked at. We have a smaller spike on the right and then a
larger spike on the left. But this time it's
analyzing this blue Canvas. So we see these pixels up
here showing that we have a spike in blue pixels
at 100% intensity. And then over here we
have both red and green, which combined to form a much larger spike
on the histogram. The same thing here. If we turn on this green Canvas, the histogram looks
exactly the same. But this time, this bar right
here represents pure green, and this one over
here on the left represents red and blue. So again, if I pull up the color picker and
we sample for green, we can see that green is
that it's full intensity. And this represents
these pixels. They're just graphing
all of the pixels that are at their full
brightness or intensity level in these pixels
right here that are being graphed are the ones that
are at zero intensity. So the red and the blue. And if we open up channel, so if we open up
the green channel, we see a giant spike
in pure green pixels. If we were to change
this to say red, we would see all
of the pixels line up on the left edge there. And that's because we don't have a single bit of
red on this image. Red is completely turned off, and this channel completely disregards any other
color information. It's only showing you
information about the intensity of red for every single
pixel in this image. If we were to say, add a little bit of
red into this image. So if I select our color
picker and I set red 255 and turn this down to zero
so we could get pure red. If I paint some red
onto this canvas, you can see up here
that we start to get a spike at the pure red
area of the histogram. So as we start to add pure
red in at its full intensity, we see the spike here. Let's turn the RGB
histogram back on. And just to summarize, the RGB histogram combines
and averages one red, two greens, and one
blue for every pixel in the image weighing
green two times because we see it as
a brighter color. And the RGB histogram
is looking at the image and graphing
the distribution of color intensity
for each one of these three primary colors
from zero at black, 255 or full intensity. Let's go try a different
experiment here. So let's go back to
our color picker. And I'm just going to
select a random color. So if I move along
the color wheel, I am not going to pick a fully saturated or fully
bright color this time. Let's say I pick
something around here, maybe a little bit more orange. Alright, so now if we look
down at our RGB values, we can see a combination of different
intensities for red, green, and blue individually. So again, all of these values for the three primary
colors are just mixing together to create literally any color
that you could imagine. These colors are just
getting mixed to create the specific color
that we're seeing up here. All close this up. What I'm gonna do is
I'm going to paint this color onto the canvas. I'm going to make this canvas
entirely our new color. Now, let's check out
our RGB histogram. Now we see three
separate spikes. The reason for that
is that we have a combination of three
different color intensities. We open our color picker backup. We can start to deconstruct what each one of these spikes mean. Despite closest to
pure intensity, is going to be the highest
number of these three numbers. Because remember this
is just a scale 0-255. This would be 212. So this would be the
red color channel. The second largest number, 171, that's going to
be our pure greens. So we see this spike
right here at 171. This represents all of
the pixels that have green at a 171 intensity level. Then we have the lower
intensity color, the darker one, which is blue. So this spike right here is
going to represent blue. Let's say that we add a, another color to our Canvas. So let's add a shade of blue. I'm just going to paint this
color on just like that. And now looking
at the histogram, we can see that it's starting to get a little
bit more complicated. So now we have six spikes. We have the three
spikes from before, which represent this
yellowish orange color. And then we have three additional spikes
that were created from the three color channels that make up this blue color. So now it starts to get a
little bit difficult to figure out which spike corresponds
to which color. You can imagine if we
have a photograph with millions and millions of pixels and millions and millions
of different colors. This RGB histogram is gonna
be extremely complex. You might be wondering
at this point, why does all of this matter? Why do you need to
understand and RGB histogram and the
different color channels. Well, the truth is that when you are editing a photograph, the RGB histogram
is something that you're probably not
gonna be using too much. You're really going to be
using the luminosity histogram to see the distribution of
tones throughout the image. But when you are
taking photographs in the field shooting
your camera, this is where an RGB histogram
is extremely important. And the reason for that is that each individual
color, so red, green, and blue, can be overexposed or
underexposed individually. You think of the entire
photo being overexposed, but you can actually overexposed one or more of these colors. If you're looking at
an RGB histogram, especially when
you're out shooting, when you can actually
correct this problem. Any of these channels are
clipped or blown out like we talked about clipping in
the previous few lessons. It can indicate that
the image is over or underexposed in that
particular channel. It might actually not be
perceptible to your eyes. But it does mean
that you've lost information in your
digital image. The histogram can be used as a tool to ensure that
you're not losing any subtle information that maybe isn't very
obvious to your eyes, at least out in the
field shooting. It's helping you to
see whether or not you've blown out any of
these color channels. Because if you've blown out or clipped any of these
color channels, you've lost detail in your image and that is something
we want to avoid. We want to capture as
much light information, as much detail as possible. Now, just like with a
luminosity histogram. So if we were to look at
the luminosity histogram for this image, which is really just
two different colors. Remember how you
learned that you want to avoid the brightest tones touching pure white and the darkest tones
touching pure black. The same thing holds
for the RGB histogram, even though it works a
little bit differently, it tells you more about
each individual color, primary color of
light in your image. And you want to avoid having
any of these channels are colors touching the right
edge of the histogram. And any of these colors
touching the left edge, especially if you didn't have any pure red, green, or blue. And the image which
you are pretty much never going to see in nature, any pure black pixels because you're
probably not going to see pure black when looking
out at a landscape. So again, you want
to avoid having any of the pixels
touching the right edge or the left edge
because that means you've lost detail
in your image. I want to jump back to the photo that we've been looking at for the last few
lessons and briefly go over an example of what
an RGB histogram looks like on a photo that has
colored channels that have been blown
out or clipped. You look up here
to the histogram. I've turned on the
RGB histogram. And if you look all the
way to the right here, you can see that this
histogram has been clipped. In other words, we have
some colors in this photo. We don't quite know
exactly what colors yet, but either red, green, or blue has been blown out. Either 12 or all of those
colors have been clipped or blown out because we see them touching the right
edge of the graph. Here. If we compare that to the
luminosity histogram, you can see that this
histogram isn't blown out. So we don't have any pixels in this image that are pure white. We do, however, have pixels in the specific
color channels. That are overexposed. So we have some colors in this image that are
individually overexposed. Again, even though the luminosity
histogram isn't clipped, we're getting additional
information about exposure from this
RGB histogram. And what it's
telling us is that I actually did
overexpose this photo. The reason for that is
because these colors or one could be two or all three of the
colors were clipped. Like we discussed in
previous lessons, whenever you clip pixels, you lose detail in that image. And that's fine. Rgb histogram can be so valuable because
with the naked eye, I can't really tell that
this photo was overexposed. But the RGB histogram
is showing me that some of the pixels are touching the right
edge of the graph, which means that I've
lost some detail. Now if I go into each
individual color channel starting with red, I can start to
piece out which one of those colors was blown out. And it looks like red is
definitely overexposed. I have pixels in this image that contain red at their
highest intensity. They are touching the
right side of this graph. In my guess would be that those pixels lie
somewhere over here. If I use my color picker and look at some
of these pixels, you can see that red
is very close to 255. The ones I've selected
here aren't exactly 255, but they're very close. So somewhere around here, I probably have pixels that
have an intensity of 255, which again corresponds
to the pixels that touch the right
edge of this graph. Let's look at some of
the other channels here. Let's go to green. And you can see here that I
have not blown out green. So green is actually within
a proper exposure level. There are no pixels
in this image that contain green at its
maximum intensity. I know that I have not lost
detail in the green channel. Let's look at Blue here. The same thing for Blue. Blue has not been overexposed, are blown out here. I have not lost any detail
in the blue channel. If I go back to
the RGB histogram, now I know that the
pixels that are touching the right edge of
this combined graph. So the average of all
three red, green, and blue channels by separating them out and
looking at them individually. Now I know that these
are red pixels up here. And that's really how you use an RGB histogram to evaluate if you've properly exposed an image by not
clipping the histogram. The other thing in RGB
histogram can help you with is when you're adjusting the
color balance of your image. If the histogram shows that one channel has a higher
peak than the others, It's possible that this
could indicate that the image has a color cast or a tint color throughout
the entire image. You can correct things
like that by adjusting the white balance and using
color correction tools. And those are more advanced
editing techniques which you may or may not be familiar with yet at this point. And if you're not, don't
worry about that now, but just so you know, when you get to the point
where you want to start adjusting white
balance and correcting colors that this is where your RGB histogram is going
to become very important. So those are the main ways that an RGB histogram
can be utilized as a really powerful tool when
you're both a shooting in the field and also when you
are editing your photos. Now, in order to
help this sink in, I really encourage
you to practice this in Photoshop at home. So open up a canvas like this. It can just be a
solid white Canvas. And open up the color picker. I want you to experiment changing the values
of the red, green, and blue channels, testing out colors at their
full intensity. And then maybe adding some different colors
onto your canvas. And looking at how
the RGB histogram correlates to the
values that you see in your color picker. And the more you do this,
the more you experiment and play around like I've shown
you throughout this lesson. The more this is going
to start to sink in, because this is very
conceptual and it's okay if it doesn't quite make
full sense at this point. But the more you play around
with this and practice, I promise that it's
going to start to make a lot more sense to you. So I hope that
really helps you out and I will see you
in the next lesson.
11. Conclusion: Well, that's it for this class. You all, I just want to thank
you so much for being here. We covered a lot, so I hope you learned a lot. I hope you took a lot of
weight in this course, and I hope you continue to practice with a lot of the tools and techniques
that you learned here. Histograms can be
a little bit of a confusing and
intimidating topic. And sometimes it can take a little while for
these concepts to sink. And I recommend that you continue to go over
the course material. And the more you study, the more you learn, it will start to make
a lot more sense. And you will start
to pick this up. Now, if you've
learned a lot from this class and enjoyed
learning with me, I definitely
recommend that you go check out some of
my other classes. They're all aimed at helping you become a better photographer, especially a better
landscape photographer, if that's the type of photography that you
are interested in. I'd also love for
you to go check out my website where
I have a ton of free resources related to photography and
exploring the outdoors. I want to thank you so
much again for being here and I hope you continue
to learn and create. And I hope to see you
back here again soon. So that's it for
now. Take care guys. I'll see you next time.