Photography Fundamentals: Understanding Depth of Field

1. Course Intro: Hi. My name is Avraham, and I've been a professional photographer for over a decade. In this skill share class, we're going to learn all about how you can control how much of your photo is in focus versus how much remains blurry, which is commonly referred to as the depth of field. When you know how to control the depth of field in your photography, you can not only signal to the viewer where to focus, but you have so much more creative choices when it comes to crafting your image. As we learn about the different methods that you can use to affect depth of field, we're going to reshoot the same subjects again using each of the different methods. That way you could see exactly how this all plays out. Additionally, at the end of each lesson, I'll provide you with examples and instructions for how you can get hands on experience yourself to really drive the ideas home. To get the maximum benefit out of this class, I recommend that you have a DSLR camera or some other camera where you have the ability to change the aperture. So if you're ready to get started, I'll see you in the next lesson. 2. General Overview: We'll begin with a general overview of depth of field explaining what is depth of field and why is it so important? Depth of field is caused by the fact that the camera can really only focus at one particular point. There's also a range that stretches both in front of and behind this point that still appears to be in focus. And that is the range that we're referring to when we say depth of field. A way that I like to think of it is like a plane or a piece of glass where the piece of glass has a thickness. Whatever's in the thickness of the glass is in focus, and the area outside the glass is blurry. When you change your depth of field, you change the thickness of that plane or the piece of glass of how much is going to be in focus. Why is being able to control depth of field so important? First of all, it gives you the creative control over your photographs. You choose how sharp and in focus the different elements will be. It gives you the ability to guide the eye of the viewer. You can choose where the viewer is going to look. In this picture, for example, the eye is immediately drawn to the weed that is in focus on the right side of the screen. While the bush on the left side of the screen doesn't get the same attention. Typically, in nature photography, photographers like to have as much as possible in focus. That is, they don't use depth of field to guide the viewer through the scene, rather they use the elements in the scene itself. However, it doesn't have to be a hard and fast rule. You can choose to have a nature photograph where depth of field does influence where the viewer looks. On the other hand, when it comes to portrait photography, photographers generally prefer to have a shallow depth of field where the subject is in focus and the background is out of focus. By learning how to control depth of field, you can decide how much of the background will be in focus or not. So in the next video, we'll go into depth explaining what influences depth of field and how you can control this important tool. 3. Controlling Depth of Field - Part 1: Perhaps the first and foremost thing that affects depth of field is the camera's aperture. Aperture refers to how open is the lens on your camera. The aperture on the lens is determined by the position of the blades. As you see in the picture here, as the blades get closer together, the amount of light that can reach the sensor of the camera becomes smaller, and as the blades move further apart, the amount of light that reaches the sensor increases. When the blades are close together, that's called closed or small aperture, and when the blades are further apart, that's an open or wide aperture. What effect does this have on depth of field? To go back to our analogy to the plane or the piece of glass. Shooting with a closed or small aperture is essentially like shooting with a very, very thick piece of glass where everything in that thickness is in focus. Whereas shooting with a wide or open aperture is like shot where there's a very thin sliver of glass whose area is in focus. Let's look at some examples to see how changing aperture affects the photograph. Here we have three objects all parallel to the camera lens. Because they are all parallel and equi distant from the camera lens, they all will be in focus. If however, we were to rearrange them so that they are staggered, then if we were to take a picture with our focus being on the nearest subject, the objects further away become more and more blurry because they are outside of that range of depth of field that is in focus. In the picture we're looking at right now, you can see from the XF data that I was shooting at an F stop of 2.8, which is rather wide open. That means that the subject in the front will be in focus, and things beyond it will fall out of focus rather quickly. In the next picture, I'm closing down my FSTop to 7.1. And here you can see how items even further away from my subject point are also now coming into focus. And then when I go down to NSTop of 13, everything is really now in focus, even though my focus point that I'm telling the camera to focus on is the subject closest to the camera, that girl. Let's put the picture side by side so you can compare at one time how the dept to feel is changing. Understanding how aperture affects depth of field is one of the most important things that you can understand. The best way to do it after you have the basic information from watching these videos is to go and do it to actually see for yourself how you can affect your depth of field in your photos. So as an assignment, before we start the next video, I want you to get out some objects and place them equal distant from each other. Then focus on either the one closest to you or the one furst away, and take pictures varying the aperture and see how that affects your photographs. I recommend shooting an aperture priority mode or manual mode when doing these exercises. If you shoot in any other mode, so the camera will actually change your aperture for you. And won't give you the control you need necessary to learn the exercise we're doing here. Have fun, and I'll see you in the next video. 4. Controlling Depth of Field - Part 2: Next thing which photographers typically do to affect the depth of field is by changing their focal distance, otherwise known as focal length. This is done by changing the zoom on your lens. When you zoom in more, you create a shallower depth of field and when you zoom out, you have a wider depth of field. Let's look at a few pictures to illustrate. In this picture here, as you can see from the XF data that I shot with a focal length of 100 millimeters. You can see that the girl, who was my subject is relatively in focus, and the other two objects are less in focus. As I increase my focal distance and now shoot at 200 millimeters, you can see that the girl is still in focus because she is my focus point. But the other two items are now more blurry. And in this last picture, would I zoom in all the way to 300 millimeters. So now you can see that the bird is much more blurry than from where we started. While many photographers will use this as a way of controlling depth of field, this may not actually be a true depth of field change. Because if you notice the girl who's the subject in all these pictures gets increasingly larger. In fact, if we were to take the original picture shot at 100 millimeters and blow it up so the subject is now the same size in the photo where the girl is shot at 300 millimeters, the blur on the bird behind would be almost the same. What's happening is that changing focal distance is magnifying the existing blur that is occurring at the current depth of field that is caused by your aperture. The aperture is still creating the depth of field, but by changing focal distance, you are magnifying the effect of that depth of field blur. Don't get me wrong. Using focal distance to create depth of field is a very, very important tool. However, realize that it must be used in tandem with changing the aperture. Before going on to the next video, I'd like you to take a few moments to take out your camera again and practice changing focal distance and seeing how that affects your photos. 5. Controlling Depth of Field - Part 3: The third factor that affects depth of field is the distance of the camera lens to the subject. By changing the distance between the lens and the subject, you are essentially changing the ratio between the lens and subject distance and the subject in background distance. I know that speaking about ratios might make your head start to spin. So let's look at some examples to make it more understandable. In next few pictures, the items are placed equal distant from each other and will not be moving. The only thing that will be moving is my camera. In this first picture, I was standing around 3 meters from the subject, the girl. And as you can see, that at an F step of 5.6, the girl and the chicken behind her are pretty much in focus, and the horse is a little less so. As I take a step forward and refocus on the girl. She is still, of course, in focus, and the chicken gets a little blurrier, and the horse even more so. In this last picture, I step even closer to the girl and refocus. Now you can see that the chicken and horse are clearly out of focus. Let's put all three pictures together so you can compare them in one view and see how even though I keep all the settings the seam in my camera, but change the camera's distance from the subject, I have affected depth of field. Now it's your turn. In order to see for yourself, how the distance from the lens to subject affects the depth of field. I want you to take some practice pictures. We have items set up equal distance from each other, and practice moving closer to the subject in each successive picture. Another thing you could do is have the subject at fixed length from your camera and only change how far the background items are from that subject. One way to do this is hold an item at arm's length from your camera as your subject, taking photos of it, and moving around, having backgrounds at different lengths from that subject. I think it would be very helpful to show you just what I'm trying to do here for this example. And so you see here we have these three cars equal distantly spaced. And what we're doing is I'm going to take taking pictures where they stay exactly the same for this first exercise, and I'm just going to get closer. So I'm going to come down and focus on the first car, and I'm showing at 5.6 aperture. So take a picture here like this. And now we get closer. Readjust for the car. You can compare how to see how they change in the depth of field. Another example that we could do is you take any of the objects and hold it and you always want to keep it the same let's take a different went easier to maneuver. This one is going to stay in the same distance from my camera all the time as I swivel around to different distances from the background. And then we can do is you can compare afterwards to see how much the background is in blur compared to the focus of the subjects that's in front of you. All right. So I hope these examples demonstrate what we're trying to do for the exercises and that you have fun learning about depth of field. 6. The Depth of Field Calculator: Till now, we've had many examples where we've seen the effects of depth of field empirically. That is, by experimenting and seeing the results. However, there are tools you could use as well to be able to accurately predict the depth of field before you start shooting. There are many depth of field calculator applications that you can have both on the computer and your phone. By entering in the type of camera you have, your focal length, the F stop you're using, and how far the subject is from the camera, you can find what the estimated depth of field will be. A tool like this can be very helpful when doing nature photography where you have time to set up. However, doing the exercises that I've outlined in the previous videos is very important for your everyday photography, and event photography, you don't have the time to enter in all these calculations. You need to have an intuitive feel for how to use your camera to get the depth of field to achieve the look that you want. Nonetheless, knowing that tools like this exists, it can be very helpful in some circumstances. I recommend that you check this tool out to see how it works. 7. Conclusion: Thank you for joining me in this Skillshare course on understanding depth of field. I hope that you've learned a lot about what causes depth of field and what techniques you can use to alter the depth of field. As a final class assignment, I'd like to see an example of you using depth of field to take a photograph. You may submit one of the practice photos from the previous videos, but I prefer if you went and took another one because practice makes perfect, and there's always more to learn about depth of field. Thanks for joining me, I look forward to seeing you in a future video.