My reply here is based on Toomas Tamm's electronic flash information http://www.chem.helsinki.fi/~toomas/photo/flash-faq.html While the information most likely applies to the internal flash in eos30, the values given here are most likely different. > 1. Is the actual duration of flash visible to the user? So if I enter the Tv > mode and select 1/60 s shutter speed, how long is the duration of a flash - most > likely less than 1/60? Is it allways constant (how much?) or does it vary in > different conditions? The duration varies depending on the power needed. With 420EX full power flash is about 2 msec, that is 1/500sec. In 2msecs the flash output has fallen to less than two stops of light (compared to maximum brightness). If less light is needed, flash circuitry cuts off the flash pulse. for example the duration at 1/8 of full power lasts only 0.4msec (1/2500). > 2. What is the actual meaning of X-sync. speed? Why would I want to set it 1/125 > with CF-9? Instead of having camera balancing ambient light with flash output when using Av mode, you want pictures taken in Av mode and flash be like the ones taken with point and shoot cameras: Sometimes there is ambient light on the background, sometimes there isnt. Actually, I don't know why one would like to set the shutter speed always to 1/125 when using flash with Av mode. one can get the same results with M mode: set time to 1/125 and select aperature. Good explanation of what is X-synch: http://www.chem.helsinki.fi/~toomas/photo/flash-faq.html#synch-general > 3. Is the brightness of the flash constant or does my camera change it in > different situations? Does the flash compensation affect this? Camera changes the amount of light output by the flash and flash compensation affects it. * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
