Flash and rear curtain sync

[gecko]

Hello all

Nikon D70 with SB600 set to rear curtain sync, M mode....

I am getting 2 flashes. One when the curtain opens and one just before it closes.

I thought I should only get a single flash just before the curtain closes.

( I have tried other settings - from memory rear curtain sync only works in M and S modes)

Am I doing something wrong?

Cheers
Gecko

[rokkstar]

If it's iTTL then the first flash is (I think) is to set the flash exposure for the actual flash. I think it's just a pre flash. Please correct me if Im wrong peeps.

[xorl]

Yep Rokkstar, you are correct. You can disable the pre-flash by not using iTTL (Eg, manual flash power) but this may not be convenient .

[gecko]

Thanks for the info

If it is a pre-flash, is it acutally happening before the shutter opens then?

I am just finishing work now and so I will have to go home and continue playing around with it.

Cheers
Gecko

[xorl]

Yes, the preflash occurs before the shutter opens. The camera uses the data gathered from the preflash to guess how much power is really required from the flash to expose the scene correctly.