Being a family with more than one Canon camera, we were able to test this 'problem' with a 40D, 60D, 7D and the 5D-III.
Guess what? All four do this... BUT you must have the cameras set to Program/AV/TV mode for it to occur. I will say again, if you have already half pressed your shutter button to focus, you aren't going to be reaching to push the LCD light on the LCD panel. It's a futz, a non-issue.
It's not, I repeat NOT, a light leak, it's the cameras trying to lock onto or find a light source to meter for exposure. It does this whether the lens cap, body cap is on or not.
Guess what? All four do this... BUT you must have the cameras set to Program/AV/TV mode for it to occur. I will say again, if you have already half pressed your shutter button to focus, you aren't going to be reaching to push the LCD light on the LCD panel. It's a futz, a non-issue.
It's not, I repeat NOT, a light leak, it's the cameras trying to lock onto or find a light source to meter for exposure. It does this whether the lens cap, body cap is on or not.