2 flashs when using rear flash

[oli_jean]

I want to know how to get rid of the first flash when using a sb-800 on rear flash mode with a long exposure.
I get 2 flash,one at the start of the exposure and the second one at the end.
I just want the second one.

Thanks

[Dennis_Vied]

Then I think you need to use manual or AA mode, because I think what you are seeing is the preflash which the camera uses to set the final exposure. The second flash is the exposure flash, the first flash(es) are what the camera and flash use to set the final exposure. If you don't want it, then use manual or AA mode.

[DouglasUrner]

I just wanted to point out -- in case it wasn't obvious -- that the first flash happens before the shutter opens.

Doug