D300 rear curtain synch

<p>Hi all<br>

I was just playing with rear curtain synch setting on my D300 with SB600 and what gets me is the fact that flash fires twice first at the beginning of the exposure and second time at the end. I have the flash gun set to TTL<br>

TTL BL however when I set it to manual it fires at the end of exposure like I would expect it to do<br>

oh and my camera is set to M and I use Shutter of 1"<br>

am I doing something wrong or is it just the nature of the beast?</p>

<p>Thank you.</p>

<p>The flash fires only once at the end of the exposure. The other flash you saw is the pre-flash; that is before the exposure.</p>

<p>Shun What does that pre flash do? is there a way to turn it off ? and it does not pre flashes when I set flash to manual is that normal?<br>

you see I have never used that function before.</p>

<p>Pre flash is required if you use TTL flash on DSLRs because the digital sensor does not reflect light as film does so that you cannot measure exposure while the shutter is open as Nikon used to do with film TTL flash.</p>

<p>See photo.net's Nikon i-TTL flash guide for more details: <a href="http://www.photo.net/equipment/nikon/guide-to-ttl-flashes/">http://www.photo.net/equipment/nikon/guide-to-ttl-flashes/</a></p>

<p>Thank you Shun great article<br>

Thanx again</p>

 

<p>This subject has been covered before, but a repeat might be appropriate.<br>

The pre flash may be eliminated by programing either of the function buttons<br>

on the D300 to FV Lock. Good for a given situation; critters do flinch at the<br>

pre flash. See page 180 of the D300 manual.</p>

 

<p>Gable Ray: even though the FV Lock, you will still need one pre-flash to determine the amount of flash needed. As long as you want to use TTL flash on a Nikon DSLR, some type of pre-flash is unavoidable.</p>

<p>The problem is that the SB-600 does not have the A mode (unlike the SB-800 and SB-900). So if Kris does not want the pre-flash, you need to set the flash manually or get a different flash.</p>

<p>Does this pre flash contribute to the exposure itself?</p>

<p>Kris, in i-TTL, the pre-flash occurs before the mirror goes up and the metering is performed inside the viewfinder. Therefore, the pre-flash cannot possibly contribute to the exposure. Again, you need to read the rest of my article. :-)</p>

<p>Great article, very informative.</p>