optically triggered strobe doesn't illuminate image - SD500 - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum
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optically triggered strobe doesn't illuminate image - SD500

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Offline SteveNosko

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optically triggered strobe doesn't illuminate image - SD500
« on: 01 / May / 2010, 19:15:36 »
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Does anyone know why these cameras will not "see" a remote, camera flash-triggered strobe flash?  Bums me out completely.

The remote strobe's light does not register on the image.  UNLESS I manually flash it during a long timed shutter.

On this puppy, I initially thought that the camera closes the "shutter" immediately after the internal flash and before the slave can fire.   These must obviously be an electronic "shutter" on the CCD (or whatever image sensor they have)

I have a SD500 and when I found out about CHDK I thought that I would now be able to slow the shutter and get the slave to register just like the old X sync setting on SLRs.  SLRs would first fully open the shutter (usually at 1/60th), then trigger the high speed (strobe) flash.
However, when I override the shutter speed down to even 1 second, the slave fires from the internal flash, but the image doesn't show it (doesn't record any of its light)! 
The internal flash fires at the beginning of the 1 second, firing the salve, but the image has no record of the slave. 

What the heck is going on here??  Could it be that the shutter still closes right after the internal flash fires then opens again for the time exposure - just so slaves won't work?

I think I hid my email so if you HAVE an answer, please also respond to K9DCI  at
arrl  dot org.   OR   via my web page Contact.

I may have to do some experimental pictures, or set up a photo sensor on an o-scope to see, or even do some laser image photos to figure out if the shutter does this open-close-open thing...to see it I can figure this out.


-- 73, Steve, K9DCI   USN (Vet) MOT (Ret) Ham (Yet)

  http://k9dci.home.comcast.net/
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73, Steve, K9DCI   USN (Vet) MOT (Ret) Ham (Yet)
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Offline Microfunguy

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Re: optically triggered strobe doesn't illuminate image - SD500
« Reply #1 on: 01 / May / 2010, 19:45:26 »
Quote from: SteveNosko on 01 / May / 2010, 19:15:36
What the heck is going on here??  


Does your slave flash ignore the camera preflash and trigger on the main flash  ... because that is what it has to do ?


David
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Offline hotvedt

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Re: optically triggered strobe doesn't illuminate image - SD500
« Reply #2 on: 02 / May / 2010, 03:31:15 »
Does this camera have a M manual mode? I have tried S2IS, A540 and SX110IS, and they all seems to work with a slaveflash in M-mode, but not in the automatic ones.
I think they omit the preflash in manual mode.
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Offline Microfunguy

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Re: optically triggered strobe doesn't illuminate image - SD500
« Reply #3 on: 02 / May / 2010, 05:12:23 »
Quote from: hotvedt on 02 / May / 2010, 03:31:15
I think they omit the preflash in manual mode.

Yes, a number of people using two cameras for stereo have reported that works.
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Offline PhyrePhoX

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Re: optically triggered strobe doesn't illuminate image - SD500
« Reply #4 on: 02 / May / 2010, 21:30:22 »
you can disable preflash in automatic modes by using the chdk flash manual feature.
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