On 5/11/07, Mat Hayashibara <[EMAIL PROTECTED]> wrote:
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.
Mat, Exactly! 1/200 is the documented X-Sync speed of the EOS 5D,
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.
It *is* a bug because at the X-sync speed of 1/200 FP flash is not needed, given that -as you correctly stated-, the shutter is fully open. And indeed, the flash range decreases dramatically when it's actually not expected. -greetings, Gerard. * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
