I do not remember where I first heard or read about this, but it was sometime back.  It is a concept of meshing tonal values with its background.  It was using Rembrandt’s “The Mill” as an example.  It avoids the striking appearance of values conflicting with each other by allowing you to soften some edges and emphasizing others.

In the painting, Rembrandt painted the windmill vanes with strict concern to their surrounding values.  Each vane represents one of all of the tonal arrangements.  I hand sketched the windmill and the tonal arrangements and posted it on my cork board in my studio and have referred to it often.

It represents:

• Light values against light values.
• Light values against dark values.
• Dark values against light values.
• Dark values against dark values.