18th October 2003, 11:27 AM
2nd Curtain Sync question
I was playing around with the 2nd curtain sync feature at different shutter speed when i realised that the flash emits 2 burst when the shutter speed gets rather low (2 sec), cannot see the difference at higher speed of 1/60 and above . It emits 1 flash in sync with the 1st shutter curtain then another at the 2nd curtain. I thought the flash is suppose to go off only at the 2nd curtain? I have read the manual already but no mention of 2 flash outputs at all.
Wont 2 outputs end up with the subject being "captured" twice or does it?
Thank u for ur advises
18th October 2003, 12:06 PM
Actually there are always 2 flashes - the pre-flash (used by the E-TTL system to calculate the actual exposure) followed by the actual flash, during the exposure.
In first curtain sync, the actual flash always immediately follows the pre-flash, so you never notice that there are 2 flashes, because the interval is too short for the human eye to notice (but if you use an external flash on the G2/G3/G5, you will be able to notice a double flash).
In second curtain sync, the pre-flash will fire as usual, but the actual flash will fire only when the shutter is about to close. If the shutter speed is fast, the interval is too short for you to notice. If the shutter speed is slow (as you have noticed), you will see the preflash fire first, followed by the actual flash when the shutter finally closes. Try this at 1s or 2s shutter speed. Or you can set it at 4s shutter speed and switch off the flash before the second flash fires. When you look at the picture, it will be very underexposed because the pre-flash does not illuminate the exposure. Not sure if this will damage anything, though, so try it only at your own risk.
18th October 2003, 12:20 PM