I have been messing around with my flash trying to get second curtain sync to work. ; I have changed the custom functions on the camera to second curtain syn, Canon 5D, attached my flash and booom--flash fires with the first curtain. ; My flash, 580EX, as a mode >>> and when I put it to that mode I get a flash at each curtain. ; OK, what am I doing wrong?
Yeah, that first flash confused me as well. ; Glad you figured it out. ; For those interested, even in Rear sync (2nd curtain) mode, the flash puts out a short burst when the shutter button is clicked to help in getting exposure correctly. ; It will still fire first just before the shutter closes so you'll get those neat rear sync effects.
I did discover that if the camera is in manual mode and the flash is in manual mode you do not get the first flash.