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  1. #11
    Erik Petersson's Avatar
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    You are right Eddy. However, I do not plan to spend money on a voltmeter for which I will not have other use. Better instead to save them for a TTL-flash for my F3, when I stumble upon one.

  2. #12
    RalphLambrecht's Avatar
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    Quote Originally Posted by Erik Petersson View Post
    You are right Eddy. However, I do not plan to spend money on a voltmeter for which I will not have other use. Better instead to save them for a TTL-flash for my F3, when I stumble upon one.
    Just wait until you get the bill for all these suggestions!
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  3. #13
    Erik Petersson's Avatar
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    I thought I paid that already. Or was that the heating bill?

  4. #14
    Steve Smith's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    must be a typo on their part. They must mean 25V.
    I think 250 volts is correct as most flashes in the Nikon F3/4 era would have had sync. voltages a lot higher than 25 volts.

    Quote Originally Posted by RalphLambrecht View Post
    Hardly any flash has a trigger voltage as high as 250V, but 250V will definitely fry your digital SLR. According to ISO 10330, all cameras must accept trigger voltages of up to 24V.
    Most DSLRs are o.k. up to 250 volts (my D100 was and I think all subsequent Nikons are rated at 250V too) and many flashes have sync. voltages in the 100 - 200 range.

    Before digital appeared, no one even thought about it. They bought a flash and connected it to their camera and used it with no problems.

    There is currently some thinking that some DSLRs are only safe up to 6 volts. I think this is largely a myth for two reasons.

    First, any competent camera designer would include an opto-triac or thyristor in the sync. circuit. These do not exist with such a low maximum voltage.

    Secondly, some people have stated that a high voltage flash is o.k. on a PC connector but not the hotshoe (of the same camera). I think this is nonesense too as they would both either be wired together or have similarly specified circuits.

    My thinking is that the manufacturers are dissuading people from using high sync. voltage flashes on hot shoes due to a fear of the centre pin touching one of the other communication pins when sliding a charged flash onto a hot shoe and damaging some other part of the circuit rather than the sync circuit itself being damaged.

    It could also be a bit of sales propaganda to get people to buy new 'safe' flashes when they buy a new camera.


    Steve.
    Last edited by Steve Smith; 01-04-2010 at 12:25 PM. Click to view previous post history.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  5. #15
    Steve Smith's Avatar
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    Quote Originally Posted by eddym View Post
    It's really easy if you have a voltmeter; just measure across the contacts of the flash as you trigger it. I've tested all of mine, just to be sure.
    Don't fire it - Just let it charge until the ready light is on and measure it. At the point of firing, the voltage will be (close to) zero as the sync. contacts short out.

    Most flashes have a circuit consisting of a high resistance (about 1M) charging a low value capacitor (about 10nF) from the main HV supply. The sync. contacts short this charge into the trigger transformer which produces a high voltage pulse which ionises the xenon in the flash tube causing it to conduct. Unless it is stopped by another circuit (auto/TTL/etc.) it will continue conducting until the main HV capacitor is empty. At this point it will stop drawing current and the HV supply will start to charge the main capacitor again closely followed by the little capacitor in the sync. circuit.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  6. #16
    RalphLambrecht's Avatar
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    Quote Originally Posted by Steve Smith View Post
    I think 250 volts is correct as most flashes in the Nikon F3/4 era would have had sync. voltages a lot higher than 25 volts.
    Steve

    I really don't know but a couple of things don't seem to add up:

    1. This website lists a lot of trigger voltages and I can't find a single one at or above 250V. http://www.botzilla.com/photo/strobeVolts.html

    2. I'm looking at ISO 10330:1992. It limits electronic flash trigger voltages to 24 V and sets this value as the camera minimum.

    Any thoughts?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  7. #17
    eddym's Avatar
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    Quote Originally Posted by Steve Smith View Post
    Don't fire it - Just let it charge until the ready light is on and measure it. At the point of firing, the voltage will be (close to) zero as the sync. contacts short out.
    Come to think of it, you're right. What I'm remembering is that it's hard to touch the probes to the pc connectors for a reading without firing the flash. With a shoe mount it's easier. I was checking the pc's on my Sunpak 622 and my Calumet Travellites, and they were always firing accidentally.
    Eddy McDonald
    www.fotoartes.com
    Eschew defenestration!

  8. #18
    RalphLambrecht's Avatar
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    Quote Originally Posted by Steve Smith View Post
    Don't fire it - Just let it charge until the ready light is on and measure it. At the point of firing, the voltage will be (close to) zero as the sync. contacts short out...
    Steve

    Would it help to connect the voltage meter to the flash contacts with, let's say, crocodile clamps, and then, give the flash time to charge up before taking a reading?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #19
    MattKing's Avatar
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    FWIW, I had some work done in 2006 on one of my Olympus flashes (3 foot drop on to tile floor = broken shoe) and the repair technician was saying then that they were doing a thriving business repairing digital and newer film cameras that had suffered damage when an older, higher voltage flash was connected.

    I had a Metz 202 flash until recently, and the 200+ volt trigger voltage is one I wouldn't even consider using with my Mamiya 645 Pro (my newest camera with a flash shoe or synch socket).

    Matt

  10. #20

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    Quote Originally Posted by RalphLambrecht View Post
    This must be a typo on their part. They must mean 25V. Hardly any flash has a trigger voltage as high as 250V, but 250V will definitely fry your digital SLR. According to ISO 10330, all cameras must accept trigger voltages of up to 24V. Unfortunately, not all cameras manufacturers stick to that, and flash manufacturers exceed it.
    Older studio flash could hit that 250V threshold no problem.
    Heavily sedated for your protection.

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