I have noticed that when using my 300D with my 580EX in high-speed sync mode I sometimes get a grossly over-exposed band on the left in portrait orientation or on the top in landscape orientation. Worn shutter, flash malfunction, body malfunction, communication error between flash and body, confusion between normal flash synchronization and high-speed flash synchronization, excessive shutter speed in normal flash sync ? I posted my problem on Photo.net but the answers were inconclusive. I am left scratching my head about it and I can’t even find out how to reproduce the result reliably… For now my bets are on user error…

Here are a few frames featuring the overexposed band in case they remind someone of a known problem. One of the most likely root causes is the somewhat loose flash hostshoe.