Flash sync & voltage hazard

Discussion in 'Photography' started by Richard H., Oct 10, 2005.

  1. Richard H.

    Richard H. Guest

    I've just become aware of an "issue" with over-voltage on the flash sync
    ports. Apparently external flashes (namely studio strobes) can damage
    the camera by feeding too much juice through the sync port.

    Is this a real danger, or one that's been concocted to sell adapters
    like these:

    On one hand, Nikon makes references to this in their docs (conveniently
    recommending only Nikon flashes as the fix). On the other hand, if this
    is a serious hazard, why isn't the protection being built into cameras?

    Does anyone have first-hand experience with this issue, and is it
    widespread / random / limited to cheap strobes?

    Richard H., Oct 10, 2005
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  2. Richard H.

    Colin D Guest

    You can believe it. Flash trigger voltages range from a few volts, <6
    or so, up to around 300 volts, specially for older units designed to
    work with mechanical shutters using mechanical switch points to fire the

    Modern cameras use solid-state switches composed of transistors or
    integrated circuits which cannot stand high trigger voltages. There are
    some cameras that apparently can withstand up to about 250 volts,
    usually high-end pro cameras.
    Business reasons. Nikon, Canon, and other camera manufacturers produce
    their own flash units, and they are not interested in making cameras to
    use or tolerate third-party units. Third-party units exist, usually a
    bit cheaper than the genuine article,but they are designed to fit
    specific cameras. An example is the Sigma 500-series units, one model
    for Canon, another for Nikon, etc. But trying to use an older unit on a
    modern camera can cause considerable grief if you don't measure the
    trigger voltage and ensure the camera can handle it.

    Further, digital cameras use a form of low-power pre-flash to measure
    the required exposure, known as e-ttl and e-ttl II for Canon cameras - I
    am not familiar with Nikons but I believe they use a similar system, so
    even if an older unit's trigger voltage is within the camera range, you
    can only use it with the camera in manual mode, since the camera cannot
    meter the flash exposure.

    If you are wanting to use a flash, my advice is to bite the bullet and
    buy the one for your camera.

    Colin D.
    Colin D, Oct 10, 2005
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  3. Yes, it's legitimate.
    Not necessarily cheap units, but also old ones. My Photogenic
    Flashmasters from the studio days require some kind of isolation. I use
    a Quantum radio slave.
    Randall Ainsworth, Oct 10, 2005
  4. Richard H.

    Richard H. Guest


    Got it, thanks. Actually, I'm on board with the technical "could this
    happen" angle. What I'm wondering (and wasn't clear enough) is, how
    real is this hazard with today's flash gear, particularly studio strobes?

    I.e., is it necessary to check this spec on everything you buy / use, or
    did the industry shift 15+ years ago with the advent of AF cameras
    (making this a non-issue with modern gear)?

    It took stumbling across this one-liner in a manual and then Googling to
    even become aware of the issue. It makes sense technically, but since
    it isn't discussed much (and only Wein seems to make a product to
    address it) I question whether it's a practical concern.

    Richard H., Oct 11, 2005
  5. Richard H.

    im950 Guest

    I didn't believe it at first, either. I tested all of my old flashes,
    AND my studio strobes, and found that some of them had over 300 volts
    going through the shoe. I now honestly believe that an old flash can do
    a lot of damage in a hurry if connected to a shoe meant for 5 or 6
    volts. I bought an adapter, and run my studio lights through it.
    im950, Oct 12, 2005
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