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11-17-2009, 01:41 PM   #1
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K20-D pre-flash eek:

Hey, 'taxians!

Well, I upgraded to a K20-D and I'm still struggling to learn about all the features.

Can anyone please tell me (or refer me to the right area in the manual) how to turn off the "pre-flash" anti-red-eye feature of the built-in flash? Even when I turn off red-eye suppression in the Functions menu, the flash still makes like a basketball player...it dribbles before it shoots.

I plan to use this rig for event photography with a pole-mounted Vivitar 285 and mini-slave triggered by the built-in flash, which will be softened by a Gary Fong Puffer diffuser. As the rig is currently set, the pre-flash occasionally fires the Vivitar before the shutter fires. I can use a cable like I did with my K10-D but the reliability was sketchy or I could use a Radio Popper but then I'd need to put a bracket on the body to hold a second Vivitar, since the RP transmitter would then live on the hot shoe.

Does anyone know how to accomplish this?

Sig:

11-17-2009, 02:16 PM   #2
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Could the issue be that your flash is firing to help the camera focus? That would be my best guess, but I wouldn't know how to turn it off.
11-17-2009, 04:31 PM   #3
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Try manual focus?

That sounds like a possibility. When I get home, I'll try the set up with the focus set to manual. If I get a clean, single flash from the built-in, the idea will be proven and I'll see if I can work my way around it...I'd still like to use auto focus if I can. If not, maybe I can ramp up the flash power and use a wide lens at a small aperture to increase the depth of field.

Thanks for the suggestion.

Sig

Last edited by Sigmoid; 11-17-2009 at 04:33 PM. Reason: Language
11-17-2009, 04:43 PM   #4
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You could shoot in manual too. Open the flash and set it to (on) and the power to -2 if you don't want it to show up in the shot much. I think it only flash focus assists in some of the auto modes. I never really come out of manual mode so I can't say which ones.

11-17-2009, 04:53 PM   #5
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QuoteOriginally posted by Sigmoid Quote
That sounds like a possibility. When I get home, I'll try the set up with the focus set to manual. If I get a clean, single flash from the built-in, the idea will be proven and I'll see if I can work my way around it...I'd still like to use auto focus if I can. If not, maybe I can ramp up the flash power and use a wide lens at a small aperture to increase the depth of field.

Thanks for the suggestion.

Sig
My k10 manual says that if the flash is enabled (green mode, or UP) it will flash several times to assist the focus. I don't use the auto up with the flash, so have never noticed this behaviour. I would be just as annoyed as you are.

The note is in the comments on AF.S in the manual.
11-17-2009, 06:35 PM   #6
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There are several possibl reasons for pre-flash. Red-eye reduction is one, but that can be turned off on most cameras that provide red-eye reduction pre-flash. AF assist is another reason for pre-flash, and you can work around that by using MF. But still, one pre-flash burst will still be required because that's how PTTL measures exposure (and the same for all other DSLR flash systems, as far as I know). I think many modern slave units can be set to ignore the pre-flash, but perhaps not flash units that predate the digital era.
11-17-2009, 07:20 PM   #7
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QuoteOriginally posted by Marc Sabatella Quote
There are several possibl reasons for pre-flash. Red-eye reduction is one, but that can be turned off on most cameras that provide red-eye reduction pre-flash. AF assist is another reason for pre-flash, and you can work around that by using MF. But still, one pre-flash burst will still be required because that's how PTTL measures exposure (and the same for all other DSLR flash systems, as far as I know). I think many modern slave units can be set to ignore the pre-flash, but perhaps not flash units that predate the digital era.
Yes sir re... You will always get a pre-flash w/ p-TTL flashes...
11-18-2009, 12:49 AM   #8
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QuoteOriginally posted by jeffkrol Quote
Yes sir re... You will always get a pre-flash w/ p-TTL flashes...
You can have the popup flash function as a manual flash by using a lens with aperture ring in the non A setting, but this has obvious drawbacks, allthough when you just want to trigger a slave than it is often a workable sollution.

For other lenses, place a small flash in the hotshoe in manual or auto mode.

11-18-2009, 05:25 AM   #9
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Maybe you could auto focus with the flash down and then pop it up after the camera has focused.
11-18-2009, 09:13 AM   #10
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Thanks to all commentors...

...for your valuable ideas.

Based on your input, I investigated and found that the "pre-flash" I experienced was actually a fairly steady beam of light that only flickered when I failed to keep steady pressure on the half-press of the shutter button. This steady light did not trip the slave and fire my secondary flash.

As far as a non-A MF lens, I think my Richonen 50mm f1.7 may be just the ticket...crank it down to f16 and ramp up the Vivitar power to compensate. I'll test both approaches and see what works best.

Thanks again for all the useful comments.

Sig

Last edited by Sigmoid; 11-18-2009 at 09:16 AM. Reason: Typo
11-18-2009, 09:18 AM   #11
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QuoteOriginally posted by Sigmoid Quote
...for your valuable ideas.

Based on your input, I investigated and found that the "pre-flash" I experienced was actually a fairly steady beam of light that only flickered when I failed to keep steady pressure on the half-press of the shutter button. This steady light did not trip the slave and fire my secondary flash.

As far as a non-A MF lens, I think my Richonen 50mm f1.7 may be just the ticket...crank it down to f16 and ramp up the Vivitar power to compensate. I'll test both approaches and see what works best.

Thanks again for all the useful comments.

Sig
The internal flash will fire at full power with a non-A aperture setting, but the guide number on my k10 is only 11 (meters, ISO 100) so it is a wimp. One could always use a card to bounce in internal flash up to the ceiling if it is bothersome, I suppose.
11-18-2009, 04:27 PM   #12
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Can also turn off focu assist by using AFC
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