Yes, theres a bunch of threads, but i just want to make sure i understand it clearly.

To avoid gain you use Tv mode, set you shutter, aim your camera at a bright light so it fills the lens, lock the exposure, With the exposure being locked at 0 and now looking at your subject everything that was dark before is now a very dark and crisp black. Right now at 0 there is no gain, and everytime you up the exposure +1 it adds 1.5dB of gain.