This never ceases to amaze me. Was just using Compressor, cropped out a letterbox, checked the preview, and I was wondering why the footage looked brighter in the encoding preview. The illusion of color perception/contast (the letterboxed version had black letterbox bars, and dragging the slider in the preview window removes the black bars).
Here's an interesting article:
[
www.psy.ritsumei.ac.jp]
www.strypesinpost.com