For a long time, I've been studying the "catchlight" patterns in a number of publications - mainly fashiom mags - as a rough indicatication of the light setups. As it would be with plain spherical Christmas tree onaments (or hubcaps) the eye reflections indicate light positioning; form (umbrellas are VERY common) - softboxes and their size; and to a degree, intensity.

What frosts my cookie is greatly differing catchlight patterns in the eyes of more than one model in a single frame. Obviously a montage of separate images - unless someone has devised a method "erasing and adding" - similar to a portrait taken outdoors with two or more suns in the sky.