Pre-flash when using rear sync?

[chawn_crawley]

<p>I have a D300 and an Sb-800 mounted to the hot shoe. When I set the camera to rear-sync, the strobe fires a burst of light at the beginning of the exposure, then again at the end of the exposure. I messed with a lot of settings but I cannot seem to find out why this is. I thought that rear-curtain sync meant only a single flash at the end of the exposure-is this not correct?</p>

<p>Secondly, when in aperture priority or Program modes, the camera forces me to only select slow-rear when I select rear. Is this a given or is there a setting I have wrong for this, as well?</p>

<p>Thanks,</p>

<p>Chawn</p>

[tommyinca]

<p>No, 2nd curtain sync means the actual flash fired and sync to the rear shutter curtain. Pre-flash happens before the shutter (1st curtain) open. If not, it will become a multiple strobes flash function.</p>

[chawn_crawley]

<p>Do you mean to say that these 2 flashes are correct operation for the rear curtain mode? Sorry, I'm just trying to get this clear...</p>

[sattler123]

<p>Yes, there is always a pre-flash and then the actual 2nd curtain flash - it is normal!</p>

[ellis_vener_photography]

<p>The preflash is for the i-TTL metering to do its thing.</p>

[frank_skomial]

<p>.. and read warnings on page 176 and 176 of D300 manual about this mode.<br>

also perhaps the PC sync socket would get disbled on the D300 body, depending on mode, speed, etc. just try to see what does not work, or how much light you loose.</p>