color correction in MeGUI

[codemaster]

When I encoded a dvd using MeGUI, I saw an option called "Color Correction" wich was on by default.

My question is: what is this option for, and in what cases it should be on?

I left it on, because it was on by default, and I wasn't sure if it produces some kind of lossy colorspace conversion that is not needed...

[poisondeathray]

Should be disabled. It toggles the colormatrix filter
http://avisynth.org.ru/docs/english/externalfilters/colormatrix.htm

Generally, only when you go SD=> HD or HD=>SD should you use it, and if you use it you should set the parameters specifically