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12-05-2010, 04:36 PM   #1
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optical slave flash help


I am trying to "fill flash" with an on camera flash and an off camera optically triggered slave flash (K10d and a Phoenix D91-BZS). The flash is capable of sensing the pre flash and waiting for the main flash. I have tested this and believe that it is correct.

The problem I am having is that when the camera triggers the off camera flash ( I see it pop), the picture (down a long hallway) is darker than when I just use the on camera flash by itself. It appears that the off camera flash fools the camera's PTTL sensing system and gets it to turn off too early.

Any thoughts would be appreciated.


12-05-2010, 06:21 PM   #2
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The P-TTL system is supposed to fire a pre-flash for metering, figure out a power setting for the flash controlled by the camera, then take the photo with that setting. So your off-camera slave flash would only alter the P-TTL exposure if it fired during the pre-flash.

What I don't know about flash could fill a book, so that's as far as I'll go for now.
12-05-2010, 06:46 PM   #3
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Almost sounds like your off camera flash is actually triggering on the pre-flash and not recharging for the actual flash and leaving your photo under exposed.
12-06-2010, 12:43 PM   #4
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Thanks for Just1moredave and jimH. I tried it again and found and fixed 2 problems. I set the flash up in detect mode, previously I set it in 2 flashes mode, and I also found that the flash has a difficult time in brighter light.

I went inside for a couple of test shots and it works.

03-26-2011, 11:07 AM   #5
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Location: San Salvador
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Eso mismo me pasa a mi... como que disparara un preflash inicial.. y luego ya no dispara el flash principal y las fotos salen oscuras.....

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