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Flash Problem

Discussion in 'Help Team' started by PJMorley, Apr 17, 2001.

  1. PJMorley

    PJMorley Well-Known Member

    I've been trying to trigger an off camera flash gun from the internal flash on my Olympus E10... So far I have tried one of those photoelectric switches attached to a Jessops 300 AF-CA.. (which is a Canon dedicated unit) hoping the internal flash of the Olympus would trigger the unit to fire the Jessops flash. which it does...

    Now the flash seems to trigger OK but surprisingly.. the pics turn out underexposed in manual and aperture priority mode when the external flash is triggered. In the other modes the scenes are well exposed but it's obvious that the external flash has had no effect whatsoever so thus far I have worked out that the camera needs to be in manual or aperture priority to work with the external flash. I've tried every combination of aperture and ISO setting etc. but nothing changes the fact that the on camera flash on its own has good exposure but when both flashes fire there is much underexposure in the resulting image...

    I imagined the oposite would have been true.. i.e. that the images would be quite overexposed. I don't understand it.

    Any ideas what is happening here?

    I've been pondering this problem for days now and the only sensible explanation I can think of is that possibly the E10 fires a preflash for exposure calculation (the preflash fires the external flash) and takes its reading from the scene lit up by the external flash. By the time the picture is taken, the external flash has switched off again and the E10 captures the now much darker scene at the reading it took hence the image is severely underexposed.

    Somebody please help me. I'm tearing my hair out here, not that I have much to start with..

    John
     
  2. David Stout

    David Stout Well-Known Member

    John

    Sounds similar to what I experienced using some Xtralites to fill shadow areas when I using a dedicated on-camera flash with my D30. The results looked awful and was due to the circumstances you describe in your last paragraph. Film cameras used to use off the film flash metering which would probably work fine but digital cameras can't work this way so they calculate exposure by a pre-flash. This triggers the slaves which discharge all their energy so, unlike the camera flash, they don't have anything saved for the main flash. The camera thinks that there is plenty of light so doesn't need to put so much energy into its own flash so when it does fire the slaves aren't able to contribute anything hence the under exposure.

    I would guess that manual mode on the E10 allows you to set the aperture and shutter speed but that the flash exposure is still controlled by the camera (being a bit too clever).

    Does the manual give any clues as to whether you can control the flash output? Does the camera have a hot shoe in which case a manual flashgun placed there may cause the internal flash exposure mechanism to be overridden such that you can work in proper manual mode?

    David
     
  3. PJMorley

    PJMorley Well-Known Member

    Thanks for the reply David. At least now my suspicions are confirmed by your own similar experience.

    I have read the manual cover to cover on flash and searched various websites looking for an answer. My conclusion is that a cable from the PC socket is the only solution, something I wanted to avoid really but no great hardship. And I know it will work, at least the manual says so.. <S>

    Thanks

    John
     

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