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10-03-2011, 04:17 PM   #1
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Join Date: Oct 2011
Posts: 3
Slave Flash Problem

I have a real head scratcher (for me anyhow)

I have a K200d and a Bower SFD926 Flash through a Tamron 17-50 2.8. I am trying to get my flash to work well as an optical slave with very strange results. Although the Bower fires no problem as a slave- it doesn't show in the images unless I set it to only 1/8 or 1/16th power in slave mode. Any more than that- it doesn't illuminate my images at all.

I am shooting in Manual (in my kitchen) at 50MM F2.8 and 1/180th of a second. I have tried slowing the shutter right down- but it never shows in the image. Eventually the image gets brighter but just due to the long exposure- not flash.

Is it possible the bower fires too quickly at the higher power? I'm just trying to wrap my head around this one

I have tried varying the power of the on-camera flash with no difference. Also- the bower is optical slave only. It works like a champ on the camera in PTTL FYI.

Any help understanding this is appreciated.

10-03-2011, 04:23 PM - 1 Like   #2

Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,206
This thread (particularly the threads referred to in that thread) answers your question.
10-03-2011, 04:34 PM   #3
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Join Date: Oct 2011
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Original Poster
That helps tremendously! I had not though it could have enough power to trigger a second time!

Also- I was under the impression there would be no pre-flash in full manual. Why does it happen? By my silly logic, the camera would have no need for a pre-flash when the focus is locked and in full manual... am I way off here?

I tried the 2 second delay- and sure enough the flash is triggered by a pre-flash- Thanks again- you were bang on.

Thanks very much for your help! I am a long time reader but first time poster here... I prefer to lurk alot
10-03-2011, 04:39 PM   #4

Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,206
The built-in flash always fires in p-TTL mode. In other words, there is always a preflash strobe, no matter what mode the camera is in.

The only time that the built-in flash fires only one strobe (and then it fires at full power) is when the lens is a manual lens (e.g. a lens with aperture ring that is not at A, or an M42 lens with an adapter).

10-03-2011, 05:14 PM   #5
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Join Date: Oct 2011
Posts: 3
Original Poster
Thanks again.

One more question to help me understand my camera better- Is the preflash used by the camera in full manual? Or is it just a waste of battery.

Thanks again, and sorry for my lack of knowledge. I have most basic knowledge, but I get obsessed when I don't understand things in detail
10-03-2011, 05:31 PM   #6

Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,206
QuoteOriginally posted by WhiteStar01 Quote
Is the preflash used by the camera in full manual?
The preflash strobe is for light metering. The result does get used by the camera in blending the ambient light with the light from the flash.

In general, it is a good thing. Unfortunately, Pentax does not allow a way to override the flash behavior (I believe some Nikon models do).
10-04-2011, 11:24 AM   #7

Join Date: Oct 2006
Location: Chicago suburb, IL, USA
Posts: 1,535
Hi WhiteStar,

I realize that you didn't ask, but if you want to trigger your external flash remotely with the popup, you can use a "digital" optical slave trigger, and setting your external to manual, not slave mode.

Morris DS-1 Digital Slave Trigger With Hot-Shoe Mount 11101 B&H

This type of trigger can be set to ignore the preflash and fire the external on the main flash where it will contribute to the exposure. If you don't want the popup flash to contribute to the exposure, you can use an infrared pass filter on the popup as it will block the visible spectrum coming from the popup, but pass enough infrared to trigger the slave. The cheapest and easiest source for IR pass filter material is exposed and developed color print film leader (the black part before frame #1). If you don't have any, try going to your local 1 hour photo processor and ask them if they'd give you some.

10-05-2011, 02:08 PM   #8
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Join Date: Mar 2010
Location: NewYork
Posts: 899
You could always try high voltage nizn batteries. I have heard of them frying flashes but as your is a current model, you could always contact the flash manufacture and ask if it can safely handle the voltage. PowerGenix ZR-PGX1HRAA-4B 1 Hour Quick Charger with 4 AA 1.6v NiZn Rechargeable Batteries: Electronics
I have used them in my promaster flashes and when freshly charged, the flash recycles much faster than with nimh. When they have been sitting for a while or are partially charged, they don't seem to have as much benefit but maybe still enough for your purposes. If nothing else you could give them a top off charge before shooting.


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