Attached Link: http://www.siggraph.org/education/materials/HyperGraph/color/gamma_correction/gamma_intro.html

Well in video, Gamma Correction deals with black levels and exposure lattitude. Too confusing? Here's a good link that explains Gamma Correction as it relates to images on the WWW. I hope you find it useful. ;-) FYI, I render ALL my Bryce images with Gamma Correction ON.