[Steven Sweeney]

Adrian provided the following response:

Optical red is a highly subtle and thin halo of red around a light area. The red exists not on the light object, but on the darkness around it. The use of Optical red can be found in the works of most any master, most noticeably in Rembrandt, Caravaggio, Velazquez, and Bouguereau. I prefer to apply it so that you would only notice it if you already knew to look for it. After all, optical red is merely a tool. I don't feel the need to shout, "Hey! Look! Optical red!!"

In short, optical red tricks the eye into seeing a glare, or greater intensity of light. When the sense of light has already been achieved, optical red adds a second punch, causing the light to truly appear as light.

Has this clarified things?