P-TTL pre-flash question - is it visible?

BobG · 02-13-2007, 07:35 AM

I bought a K100D in mid-December, and have recently purchased an AF360 FGZ flash to use with it. I'm new to P-TTL, and want to be certain everything is operating as it should. Is the pre-flash (when using either the built-in flash or the AF360) so fast it's not visible, or should I be able to notice it (two distinctive flashes)? I'm sure this has been asked before, but I could not find something about this. I'm assuming it's so fast I can't see it, otherwise there would be a difference in shutter lag between shooting with flash off and flash on.

*jfdavis58* · 02-13-2007, 07:42 AM

You might see it. Especially if you have a non-P-TTL flash to compare. You might also see it in the viewfinder under the right circumstances-a dark subject. It can be a bit disconcerting. There is a shutter lag-it's small. It's not two distinct flashes-more like a hesitation or a catch then full blast, or two nearly simultaneous pops. Sometimes your subject will see it, sometimes not. Dogs do after three or four pops and manage to get their eyes shut just as the shutter opens.

*Ed in GA* · 02-13-2007, 08:09 AM

I have a hard time distinguishing the pre-flash from the flash. I have both the 360 and 540 and I can't tell.

*dave kitson* · 02-13-2007, 12:04 PM

Originally Posted by BobG

I bought a K100D in mid-December, and have recently purchased an AF360 FGZ flash to use with it. I'm new to P-TTL, and want to be certain everything is operating as it should. Is the pre-flash (when using either the built-in flash or the AF360) so fast it's not visible, or should I be able to notice it (two distinctive flashes)? I'm sure this has been asked before, but I could not find something about this. I'm assuming it's so fast I can't see it, otherwise there would be a difference in shutter lag between shooting with flash off and flash on.

If you look through the viewfinder you will see the pre-flash, you will not see the main flash because the mirror will be up.

dave

*Alvin* · 02-13-2007, 12:31 PM

Originally Posted by dave kitson

If you look through the viewfinder you will see the pre-flash, you will not see the main flash because the mirror will be up.

dave

I notice the pre-flash through the viewfinder as well.

BobG · 02-14-2007, 01:00 PM

Thanks for your answers. I had not noticed the pre-flash through the viewfinder before. In P-TTL mode, with my eye tight against the viewfinder to block ambient light, the pre-flash is visible before the mirror goes up. When I put the flash in manual mode, there is no pre-flash visible in the viewfinder.

BobG

Cideway · 02-14-2007, 11:24 PM

Originally Posted by BobG

When I put the flash in manual mode, there is no pre-flash visible in the viewfinder.

BobG

That is because the flash in manual mode is functioning independantly of the cameras meter, same for A mode on a 540 or 360.

The one big issue with the Pre-flash, both with Pentax's P-TTL and Nikon's i-TTL is that there are people out there whom are quick enough to react and close their eyes from the Pre flash, so they get the stoned have closed look when the shutter opens and the main goes off. I find that from the second shot onwards of my self with any camera with a Pre-flash my eyes are closed.

The work around is to use the 2s MLU to make sure the Pre-flash goes off before the the mirro goes off and then 2 seconds later the shutter opens and the main goes off. that give people time to blink and then recompose them self, just make sure you tell them to hold their pose till after the second flash

slipchuck · 02-18-2007, 04:38 PM

Originally Posted by BobG

I bought a K100D in mid-December, and have recently purchased an AF360 FGZ flash to use with it. I'm new to P-TTL, and want to be certain everything is operating as it should. Is the pre-flash (when using either the built-in flash or the AF360) so fast it's not visible, or should I be able to notice it (two distinctive flashes)? I'm sure this has been asked before, but I could not find something about this. I'm assuming it's so fast I can't see it, otherwise there would be a difference in shutter lag between shooting with flash off and flash on.

I am not sure I am seeing it pre-flash, but I know that if I trigger a pocket flash unit, it definately fires ahead of the main flash, but ever so slightly. I have tried to take a pic of a barebulb flashing, but couldn't.
when I put my k10 in wireless mode, then I could capture the barebulb flash as I don't think the pop up flash on the k10 uses the preflash anymore, my Dg500 sigma flash does the preflash instead.

hope this makes sense

randy