>To make it very concrete: If you have FP flash active on the flash and >your shutter speed is 1/200, the flash will fire in FP flash mode >(also called 'long burning'), so instead of having a typical flash >duration of 1/10000, the flash will fire for 1/200, an exposure 5x >longer! > >The tricky side of this bug is that there's no apparent visible >difference between normal flash and FP flash. You can only observe >this bug by photographing a rapidly moving subject, like running >water.
That's NOT a bug, and if you think about it, it's the only way they can make focal plane flash work for shutter speeds greater than the inherent electronic flash sync speed of the shutter... as the curtain opening travels across the film plane, the flash fires MULTIPLE TIMES so that every portion of the frame gets the same flash exposure. It has to fire once for every width of the curtain opening as the slit progresses across the film plane. That's why the flash range decreases so much in FP/high-speed sync mode, due to the multiple discharges. The basic flash synch speed is the fastest one at which the shutter curtains are fully open and expose the entire film frame simultaneously... any faster than than, and the shutter opening is a slit travelling across the film plane formed by slightly offsetting when the first and second shutter curtains open. Life is what happens to you... While you're busy making other plans! Mat Hayashibara [EMAIL PROTECTED] * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
