I just learned about the importance of lighting placement, and the importance of not changing it. Here I am, painting a leaf. Photo on the left, painting on the right, 5000K lamp behind and above my right shoulder.
Focusing on just the green parts, you can see that the values are more or less in the right range. The green is only slightly different between the two.
Now without moving the lighting, I swapped painting and photo. Here is the result.
It looks like I've exaggerated the contrast, but I did not. These are both taken from the same distance, thirty seconds apart, with the same lighting. I just swapped the photo and the painting, left and right, so that the painting is now a few inches
further from the light.
What a difference! My values are now way too dark in these new lighting conditions. The implications of this are:
Don't move your lamp
Don't move your easel
Don't even move your painting on the easel
Don't work in daylight and at night, unless you black out all the windows
Don't pick up your photo and hold it under a lamp when checking colors
I watched Mark talk about not wearing a white shirt when painting, and I thought that sounded excessive. Nope.