Sometimes, I wish Canon had a flash system as simple as Nikon’s. I’m not saying that it’s bad, under-powered, I’m saying is not as sophisticated or as flexible as Nikon’s. When dealing with flash, you must deal with exposure compensation. Exposure compensation is topic that you have to feel, there are no hard rules.

  • The exposure compensation does NOT work in manual mode.
  • The flash exposure compensation does NOT work in manual mode (full power, ½ power…)

Canon splits the exposure compensation between the camera and the flash.

  • The ambient light exposure compensation is set on the camera.
  • The flash light exposure compensation is set on the flash.

If flash exposure compensation has been set with both the Speed lite and camera, the Speed lite’s flash exposure compensation amount will override the camera’s.

— Canon: Manual: Page 14