thanks, im not to worried bout the 'look' im more worried bout the light intake on a subject in a low light situation. Wouldn't it block the already minimal light that comes in? (lets say a simple 3 way lighting in a dark room)
Nope. A large mattebox will not reduce exposure. Exposure is based off of the light reflecting off of the scene/subject. The only thing a mattebox does is shield light from directly hitting the lens. Lens flares cause a drop in contrast and result in color shifting and revealing any imperfections of the glass.
Having a mattebox on camera will not reduce the amount of light reaching the lens from reflected sources.