T4I video lighting

Build in flash, is flash only for still pictures. As far as video light, probably best bet would be self contained unit with it's own battery and power on switch  and you would use camera's shoe for mounting purpose only and that should work fine, since it doesn't have to be synchronized to anything. Just make sure it doesn't have some high voltage there, some old flash units had high voltage triggers that would fry modern DSLR. Probably safest and easiest option would be to mount the light to the bottom, where tripod goes, using C shaped bracket. I didn't do any testing, but my guess is DSLR can have very clean video at much lower light than most consumer video cams, so video light may not be required as often, if at all.