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  1. #1
    clockdoc's Avatar
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    Question Sync'ing a servo flash

    A friend loaned me an older Osram SC18 Servo (slave/flash) to experiment with. It worked well as an off camera slave unit when triggered by my Kodak CX6330 camera's flash.

    However , when I tried to duplicate the results with my Sony F707, the flash output from the SC18 was never to be seen in any of the shots. I should add that the "red-eye' mode was turned off so all I was getting was the single burst when I depressed the shutter button.

    I then though it may be tied to shutter speed and tried various speeds in the manual mode even down to 1 second but with no luck. Have any of you had similar experiences with slave flash units that are triggered by the cameras onboard flash?

    Thanks for your help.
    Sincerely,
    Lee -clockdoc-

  2. #2
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    Hi Lee --

    Don't know if this could be your problem, but as you probably know some cameras use the flash as an auto-focus assist lamp. Could it be that a small burst fired to help with AF is your problem? I suppose you could test by turning off the AF if your camera permits.

    EL

    EDIT: Think I am off-base here. Had a quick look at the F707 specs and it doesn't seem to use the flash for AF assist. Apparently it has some kind of laser hologram setup (!).
    Last edited by ELAY; 07-19-2007 at 03:57 AM.
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  3. #3
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    EL,
    Congratulations!!! Thank you. Your comment about the auto focus assist lamp got me thinking about how the Sony F707 flash system works. While it doesn't have an autofocus lamp like the Nikons do (it uses a projected hologram pattern), your comment made me look at the flash itself. Since the Sony uses a through-the-lens (TTL) metering system for the onboard flash, it actually flashes twice. I never noticed it when taking pictures as I rarely use the onboard flash, preferring available light. The 'pre-flash' was triggering the little slave flash to go off just before the shutter opened and the primary flash went off. The Kodak CX6330 doesn't use a preflash and that is why I could take photos using the servo flash with no problems.

    I hooked up my Sony F1000 external flash to the camera. Since the F707 doesn't have a hotshoe, the flash needs to be plugged into the accessory port. For whatever reason in its design, when using the F1000, you must compute your aperture manually through testing as the TTL or preflash does not function. Once I dialed in the proper aperture for the flash distance, it worked as it should. I understand from readings on the strobist website, that some of the newer slave systems allow you to tell the slave to ingore one, two or possibly three preflashes before firing the slave.

    So there you have it! Mystery solved thanks to EL's idea regarding the autofocus lamp. Thanks again for your suggestion!
    Sincerely,
    Lee -clockdoc-

  4. #4
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    I read somewhere about a light receiver you can buy (Wein Peanut comes to mind, but I could be wrong) that is programmed to ignore the pre-flash. Goes into the PC Synch spot.

    Glad you solved your problem, though I think you are giving me too much credit for a wrong guess!

    EL

    EDIT -- I've never really tried to understand TTL so forgive me if this reveals ignorance, but could you disable the TTL function on your camera, and thus disable the pre-flash?
    Last edited by ELAY; 07-19-2007 at 08:42 PM.
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