Monitor Preflashes (SB800)

[mrbillf]

Hi All,

I'm not 100% about this question but anyway I'll attempt to ask it.

Equipment: SB800 & D200
Settings on the flash: AA and the 2 flash symbols.
Settings on the D200: basically single shot, Aperture priority at f1/250.

Going by what the SB800 Manual has said is that by setting the flash in 'Monitor preflashes (the 2 flash symbols) and AA that the camera will

"Just before the flash fires, the SB800 fires a series of imperceptible preflashes that are detected by the camera's TTL Multi- Sensor and analyzed for brightness and contrast"

Mmmm, I say. How does one trigger these preflashes? because I've tried a number of different setting on both SB800 and D200 to try and do this. Is there some sort of trick to it?

Has anyone had success with preflashes mode and what were the setting used on both SB800 and D200?

Cheers,
Bill

[Yi-P]

The SB800 when mounted on TTL flash compatible cameras will fire preflashes in TTL, TTL-BL modes, and the AA mode I think as well...

It fires up by itself when you press the shutter.

The way to eliminate this is to turn the flash into one of the manual modes. GN or M.


If you want to 'see' the preflash or try to see what it does, set your FUNC button to "FV Lock" via the menu (Controls section).

When you press the FUNC button, it will fire the preflash only and lock the flash EV output by what the camera/flash measured at that instance and will not fire any preflash to determine exposure until you tell it to do so again (cancel the FV lock).

Hope this makes sense...

[digitor]

Yes, for some reason that is beyond me, the SB800 fires preflashes in AA mode. It doesn't need to, as it's measuring the flash exposure with its own sensor. Ther's no need to do anything to trigger the preflashes - anytime the two flash symbols appear in the SB800 display, you'll get one (In my experience, a preflash is most useful for getting pictures of people with their eyes half-shut).

It's quite easy to see the preflashes - if you can see a flash through the viewfinder when taking a shot, that's the preflash.

To avoid preflashes, without having to resort to manual flash calculations, use A mode - you will get exactly the same exposure result as AA mode, with no preflash.

Cheers

[mrbillf]

Thanks Yip & digitor,

Well, I did as you suggested Yip and yeah when I set the FUNC button to FV Lock and then press the FUNC button I can then see what it does. However, I haven't seen the preflash fire at all when I press the shutter release and I'd imagine it suppose to if I've got all the settings correct, which is what you suggested (TTL, TTL-BL and AA modes). That is what you mean by fires by itself..

Hope I'm making sense.

What got me started on this was I was watching some news coverage and the photgraphers there had the preflashes going off like crazy.

Bill

[Yi-P]

Thanks Yip & digitor,

Well, I did as you suggested Yip and yeah when I set the FUNC button to FV Lock and then press the FUNC button I can then see what it does. However, I haven't seen the preflash fire at all when I press the shutter release and I'd imagine it suppose to if I've got all the settings correct, which is what you suggested (TTL, TTL-BL and AA modes). That is what you mean by fires by itself..

Hope I'm making sense.

What got me started on this was I was watching some news coverage and the photgraphers there had the preflashes going off like crazy.

Bill

The preflash is so fast that is hard to 'see' as it comes second with the main exposure flash.
Try this instead, set camera to rear sync, sync it down to 1/15 or maybe slower, you will start to notice it as its been separated by a little time before the main flash... If you fire a flash at 1/200th sec, in 1/200th sec + the 40-50ms shutter lag in the D200, you will have to notice the preflash and main flash, it is bit difficult to do so.

I'm not sure how press photogs work, but flashes you see might only be traces of other's flashes and all preflashes are included already...

[mrbillf]

Thanks Yip,

You have been most helpful. All sorted and I now understand.

Cheers,
Bill

[Steffen]

I don't mean to rub it in but to quote your own quote:

"...the SB800 fires a series of imperceptible preflashes"

Note the "imperceptible" bit.

Cheers
Steffen.