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Remote Flash Sync

Discussion in 'Canon Conflab' started by BigFoo, Jan 13, 2021.

  1. BigFoo

    BigFoo New Member


    Having just got back in to photography after many years, I'm starting off with some indoor portraits and macro. I have a problem with remote flash sync. I've searched the forums for this issue but previous posts seem to refer to pre flash being the issue.

    I have two remote flash guns triggered using light sensors (seagull type). When I use the camera's inbuilt flash to trigger these units, they do not seem to sync correctly with the camera, although this is not noticeable until looking at the image. To the naked eye, the flashes all seem to go off simultaneously. There is no pre flash from the camera. However, if I use a separate flash gun on the camera's hot shoe, this does then activate and sync with the remote flash and the images confirm this.

    I'm using a Canon 350D set in full manual mode.

    I maybe missing something fundamental but any constructive advice would be welcomed.

  2. neilt3

    neilt3 Well-Known Member

    Is the flash gun mounted to the camera also set to manual exposure rather than still being set to TTL ?
    If it's firing after the off camera flashes it sounds like it's still doing a pre-flash.
  3. PeteRob

    PeteRob Well-Known Member

    I'm only guessing. Does the 350D have infra-red focus assist? There has been a trend in cameras to use the internal flash to assist AF rather than fitting a dedicated infra-red light. The camera then pre-flashes to set focus. This could trigger external lights. Speedlights, fitted on the camera hot shoe, usually have IR-assist and the flash can be disabled so they act as a focus aid only. There is usually some visible red light emitted too.
  4. BigFoo

    BigFoo New Member

    Thanks for the replies.

    The flash on the hotshoe is manual. There is no pre flash.

    There is no focus assist and no pre flash and no IR light.

    I've done some diagnostic testing by shooting with the built in flash towards a light activated remote flash at various shutter speeds from 200th/sec down to 1 second. Although both flash units appear to be synchronised to the naked eye, not once did the remote flash appear on the shot. This would lead me to think that the remote flash is triggered before the built in flash or maybe had a much shorter flash? I must reiterate, there is no pre flash.
  5. PeteRob

    PeteRob Well-Known Member

    I found a review that said:

    "Like the first Digital Rebel, the Digital Rebel XT uses the built-in flash head as its AF-assist illuminator, rather than a bright light built into the camera's body." ​

    Try it with manual focus and manual exposure.

    Edit: I only used my 5D (same age as 350 D) with off-camera flash and an ST-E2 controller.

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