EOS Flash Photography System I'm a newcomer to flash photography, just wanna know more about fill- flash. What would be the effect if the shutter speed is longer than the flash sync speed? Shallow depth-of-field always means using a very fast shutter speed, say 1/500 and 1/1000th second. How to set the flash in conditions like portrait photography? I have also heard that the flash unit usually gives out light that is too much to be used as a fill flash. How much negative flash exposure compensation is suitable? Any reference to introductory materials on the web would be welcome. Many thanks.