Quote Originally Posted by Marko View Post
Andrew and Richard have pegged this. This sounds like a classic sync speed issue. Basically you have exceeded the maximum sync speed your flash can sync with your camera.

The exif data on any frame where the band shows will tell you what your shutter speed was for any given shot. Googling your flash's sync speed or checking the manual will tell you what the sync speed is. If the shutter speed is faster than the sync speed your problem is now solved. All you have to do is never exceed that speed and you will never see those bands.
Would that happen if your camera is set to auto and it's the camera's flash? Wish I had the camera in front of me.