What Do We Know About Shadows

If I tell you that in your painting your occlusion shadows are missing, would you know what I'm saying? 

We talk a lot about lights, but do we give enough attention to shadows?  I have a notion that if we know what to look for, we're most likely to see it.  Once we see it, we can decide how to use it in our work.  But if we don't see it, we won't consider it at all.  Consequently, our work might go lacking. 

Look at the images in this photo. 

The apple on the left works fine, but shadows are out of kilter in the one on the right.  Let's break it down into two crucial areas and show how the shadow parts missing can put it back together again 

1. Form Shadow--All areas on a shape turning away from the light source.
2. Cast Shadow--Any shadow caused by the light being blocked.

Notice how where the stem comes out of the apple the Form Shadow merges with the Cast Shadow cause by the opposite edge of the opening.

1. Core Shadow--That part of a form shadow closest to where it begins to turn away from the light source.  The Core Shadow is caused by the reflective light within the Form Shadow.
2. Occlusion Shadow--That tiny area where the shape touches a surface within which all light is shut out.

Here are our apples with all their shadows in the right places, feeling much better now.