Thanks so much for a really useful and easy to follow class, Olga!  Brilliant tips and lovely to see your wonderful art work ...

(1) This is the original photo of flower collage: 

 

(2) This is taken on my desk on a very sunny today, with a window to the right:

 

(3) This is the same position/natural light as above, but I turned the paper sideways on the desk so the light coming from the window was more evenly distributed! :

 

(4) This is the photo above, colour corrected on my phone (first time!) and cropped - and the cover shot!  The colours are how I see the piece with my eyes!