2nd-curtain sync

Hi Everyone,
I've been lurking around this forum for some time and wish I had found this place sooner. I have a question and hope will find some possible answers here.
My current gear is XTi with Sigma 17-70 lens and a Metz 48 AF-1 flash. I've set my camera to 2nd-curtain sync and when I shart shooting, the flash will go off in the beginning and then flash again before the rear curtain.
I've tried in AV and M mode both turn out the same. Is that normal or are there other settings that I did not activate?
Thanks in advance.

Vincent

I don't know about the Metz, but my 580 EX manual states that a the preflash will fire in second curtain sync when using ETTL. A preflash is normal in auto ETTL modes but is usually not noticeable, but gets fired sooner with 2nd Curtain Sync.

I don't think the preflash would go sooner, but the main flash would be later, being synched with the second curtain rather than the first. The net effect is that the separation of the two would be more noticeable, especially if the shutter speed is slow. But yes, it's almost certainly a preflash for metering purposes that you're seeing.

Madweasel wrote in post #6751638
I don't think the preflash would go sooner, but the main flash would be later

Heh! I would have put it that way if I had thought of putting it that way!

Basically, the preflash will always go off right after you press the shutter release button and before the shutter opens.
And it's the actual flash that will be at the beginning of the exposure (1st curtain sync) or at the end of the exposure (2nd curtain sync).
So if you set an exp. time of 10 sec and have the 2nd curtain sync set, it will be 10+ sec interval between the two flashes.

Thanks so much for all your quick reply. Now that I know it's from the metering, it's all good.
Thanks again.

Vincent