On Fri, 19 Mar 1999 18:59:08 -0500 Thierry PERTUY wrote: > Now if the flash fires 1/1000s, what remains mysterious to me is why does > the guide number drop from 42 at 1/60s to only 20 at 1/250s? If the flash > duration is maximum 1/1000s, why couldn't the flash give the same light > power in both cases? Now, here's a wild guess: when we say the flash duration is 1/1000 we mean the light is being -generated- for this amount of time but it does not tell us how long the light 'hangs around for' :-) Assuming the light lasts much longer than the generation period, then it's easy to understand why the guide number is so much higher when shutter speed is so much slower. Bye, Mike [EMAIL PROTECTED] www.NetworX.ie ---
