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08-12-2008, 10:31 AM   #1
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K10D Pre-flash - how to stop it?

I've used my K10D for a little over a year now, and have acquired a couple extra lenses in that time. The original was the Pentax 40mm pancake lens. Then I got the Tamron 28-300 mm f3.5-6.3 Macro. Just a couple of weeks ago I bought the Sigma 180 mm f3.5 Macro EX DG lens for the specific purpose of taking bird photos, mostly hummingbirds. This latter lens is the sharpest of all, and does a far better job than the Tamron at any zoom from 120 out to 300 mm.

However I've run into a problem that's about buffaloed me. When using the camera's pop-up flash, I can prevent it from preflashing with both the Pentax and Tamron lenses, by setting things mostly in Manual. But nothing I've tried has been able to prevent that pre-flash from firing with the Sigma 180 mm lens. This is a terrible distraction when trying to catch a hummingbird and get a sharp stop-motion shot, the pre-flash causes them to "flinch" or do a sudden turn or something to mess up the carefully planned shot.

Can anyone explain what I might be doing wrong? Or is this Sigma just going to have its way, regardless?

Thanks
Olin

08-12-2008, 10:51 AM   #2
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QuoteOriginally posted by Gooneybird Quote
However I've run into a problem that's about buffaloed me. When using the camera's pop-up flash, I can prevent it from preflashing with both the Pentax and Tamron lenses, by setting things mostly in Manual.
Using the aperture ring on the lens, any setting besides "A", is the only way to get the on board flash to not preflash. I think the Sigma 180mm has an aperture ring.

Thank you
Russell
08-12-2008, 10:58 AM   #3
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I think you need an external flash to disable P-TTL completely.
08-12-2008, 12:17 PM   #4
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QuoteOriginally posted by Russell-Evans Quote
Using the aperture ring on the lens, any setting besides "A", is the only way to get the on board flash to not preflash. I think the Sigma 180mm has an aperture ring.

Thank you
Russell
Thanks Russell. But why do not have this trouble with the Tamron and Pentax lenses? They both have the "A" and that's what it stays turned to all the time.

Olin

08-12-2008, 12:21 PM   #5
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QuoteOriginally posted by jamonation Quote
I think you need an external flash to disable P-TTL completely.
Perhaps you are correct, but from another post in the "Knowledge base" forum, I read that the K10D did not have the P-TTL capability. Frankly, I don't know if it does or does not. But regardless, why do I not have the pre-flash with my other two lenses when using all Manual settings? I don't have an external flash with those lenses.

Thanks,

Olin
08-12-2008, 12:54 PM   #6
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Are you talking about pre-flash for exposure or pre-flash for AF assist?
08-12-2008, 01:18 PM   #7
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QuoteOriginally posted by Gooneybird Quote
Thanks Russell. But why do not have this trouble with the Tamron and Pentax lenses? They both have the "A" and that's what it stays turned to all the time.
You just don't see the preflash as it is too close to the main flash. It is still there. You can prove it to yourself by setting everything that same way you did before, but instead of using whatever drive mode you were using, switch to 2 second delay. As soon as the mirror flips, you'll see the preflash, and then see the main flash when the shutter goes.

Thank you
Russell
08-12-2008, 02:08 PM   #8
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QuoteOriginally posted by Russell-Evans Quote
You just don't see the preflash as it is too close to the main flash. It is still there. You can prove it to yourself by setting everything that same way you did before, but instead of using whatever drive mode you were using, switch to 2 second delay. As soon as the mirror flips, you'll see the preflash, and then see the main flash when the shutter goes.

Thank you
Russell
By golly, you're correct. Since I'm in Manual for everything, including Focus, it does indeed have the preflash. I just tested it with the Tamron set to approx. 200 mm and as you said I did see the preflash and 2 secs. later saw the main flash. When I was using this lens to take the bird shots, the two flashes were apparently much closer together than with the Sigma 180 mm, since I could see both flashes with it and could not with the Tamron. Also, with the Sigma, the first flash spooked the birds and did not with the Tamron. But the quality of sharpness was far greater with the Sigma, and that's what I want to learn how to use to its most effectiveness. Is there any Menu item that would allow me to cancel that preflash? Thanks for your help.

Olin

08-12-2008, 02:11 PM   #9
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QuoteOriginally posted by Marc Sabatella Quote
Are you talking about pre-flash for exposure or pre-flash for AF assist?

Please see my other response. But to answer your question, I'm in Manual everything, aperture, shutter and focus. Yet still get the pre-flash, but don't want it.
08-12-2008, 02:42 PM   #10
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There is no way to turn it off. P-ttl preflash will not fire with a fully manual lens, but the flash will only fire at full power. The most practical approach is to get an inexpensive flash with an Auto setting (not TTL or P-TTL) and use that instead.
08-12-2008, 03:02 PM   #11
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QuoteOriginally posted by Gooneybird Quote
Is there any Menu item that would allow me to cancel that preflash? Thanks for your help.
Not to my knowledge.

Thank you
Russell
08-12-2008, 03:40 PM   #12
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I don't understand the pre-flash at all. I thought pre-flash is only when you set the flash to "red-eye" reduction and also for AF assist (also only if it is set to auto-flash mode, and when there is not enough light to AF). If it is manual flash, I don't think it will do pre-flash; at least, that is my understanding.
08-12-2008, 05:02 PM   #13
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QuoteOriginally posted by aleonx3 Quote
I don't understand the pre-flash at all. I thought pre-flash is only when you set the flash to "red-eye" reduction and also for AF assist (also only if it is set to auto-flash mode, and when there is not enough light to AF).
In the p-TTL system there is also a pre-flash that the camera uses in order to meter before taking the picture. In a regular (non p-) TTL system, the camera meters off the same flash that is used for the actual picture, but for various reasons, this system was deemed inappropriate for digital, even though on the camera that support it (*ist D series) it appears to work well enough.

QuoteQuote:
If it is manual flash, I don't think it will do pre-flash; at least, that is my understanding.
That's true, but we're talking about p-TLL flash, not manual flash. Just because you are in a manual focus or exposure mode on the camera doesn't mean you are limited to manual flash as well.
08-12-2008, 05:13 PM   #14
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I hate the preflash too, it makes the onboard flash more or less useless for people shots, everyone half-close their eyes and look like they are on drugs or something. It's not just pentax of course, all brands seem to be about equal. P-ttl seems to be a real step back in usability compared to proper ttl. I have a few old auto-flashes from back when I had my LX and they are still very good and surprisingly accurate. To be on the safe side I bought a Wein voltage stepper to prevent the old goldies from burning the circuits in the camera. Money well spent I think.
08-12-2008, 05:38 PM   #15
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After reading all of these, I am glad I kept my *istD as a "Back up" to my K10D.

While the K10D is a superb camera, and takes excellent photos in daylight, or in bright light, the P-TTL flash is a real pain as people here have described for wild life. I use it with an AF540FGZ to project a beam opf light out to my subject, which is usually 10-20 feet away, under the canopy of the forrest in relitive darkness. The preflash for metering and focus assist really fives me trouble.

With my *istD, which is both TTL and P-TTL capable, I use a TTL flash, specificallt the AF500FTZ. Flash shots turn out great with this camera, and the image quality at 400ISO (which gives better flash distance) is exceptional

I really believe that for a serious nature photographer, the only viable flash options are, in order of preference, TTL, full manual with calculated flash power to meet your needs, and "Auto" using the flash's built in sensor (assuming it has one)

The reason I chose this order is that I can use TTL with spot metering, and have the flash intensity perfect on the point I want. Full manual flash can be calculated to give the same result as TTL, it just takes effort and good checking of distance, It is clearly not spontaneous. Auto mode is last because the sensor on the flash has too wide a field of view to gaurantee, especially for wild life, that it is not metering off the background, which can be many feet further away, leading to over exsposure
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