Digital compatable flash guns

Discussion in 'Digital Cameras' started by MikeS, May 15, 2004.

  1. MikeS

    MikeS Guest

    Digital compatible flash guns.

    I have a Jessops 300 af-Ni twin flash which I use on my Nikon F50. It is not
    sophisticated but has served me well.

    I use it for macro work(300 mm Sigma with macro attachable lens) with the
    head pointing upwards deflected via a diffuser onto the subject. This
    diffuser is made of soft plastic which enable it to be folded down into a
    small size 3 x 4 inches it has an angled reflector inside it, which diverts
    the light forward. It is held onto the flash gun with Velcro.

    I have since bought a Nikon D70 and want to know if it is safe to use it on
    my D70?

    I have tested my flash gun voltage readings at the terminals that connect it
    to the camera and they are as follows 14, 9. and 5 volts. Bearing mind when
    a flash gun is triggered it has to discharge a high voltage across the flash
    lamp. I cant see why a high voltage is required at the camera terminals. As
    I believe this is what happens then you switch a flash gun on. First it
    charges a capacitor via a step up transformer which produces a high voltage,
    in order to fire the flash tube, in order to do this, one must complete a
    circuit. this circuit surly cannot be actually in the camera it must be set
    of via thermistor which has a low voltage trigger circuit which is in the
    flash gun. Could you imagine haveing 250 volts on terminatls that could be
    touched by the user.

    My question is, doe anyone know what the terminals trigger the flash on a
    Nikon flash gun and which terminals are used to talk to the flash gun and
    get info from as it its state of charge etc.

    Regards MikeS
    MikeS, May 15, 2004
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  2. MikeS

    Smarty Guest


    There are a total of 5 terminals in the hot shoe, including the external
    bracket which is chassis ground / earth (if you are British!) to which all
    other signals / comments of mine are referenced. The center large terminal
    is the "X" contact which goes to ground when the flash is fired. The "Q"
    terminal which sits at around 5 o'clock quenches the flash when the (analog)
    through-the-lens sensor determines that sufficient light has reached the
    film plane / imaging CCD. The "Ready" terminal at around 7 o'clock goes high
    to indicate that the flash has enough energy to initiate a burst, and is
    often used in the camera body to turn on a lightning bolt or other display
    to indicate the status of the flashgun. The final terminal at about 1 oclock
    indicates that the hot shoe senses an attached flash. (This could be
    inferred from the Ready terminal also but only after the capacitor has
    completely charged.)

    The entire description above is for a classical Nikon flash with analog TTL
    protocol / metering only. No support is this description for the more recent
    digital TTL (D-TTL) which provides a data link for more complex statusing,
    control, etc., nor does it even attempt to cover the i-TTL (latest format)
    hot shoe, which is not described in any place I can find it.

    The method most commonly used to isolate the trigger circuit from the hot
    shoe uses a thyristor (not a thermistor) which is an electronic switch which
    permits large current switching while isolating the input trigger. The newer
    Nikon flashes use an insulated barrier gate transistor.

    I would not speculate as to whether your specific flash is safe to try or

    I can provide you with more technical details if this would help.
    Smarty, May 16, 2004
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  3. MikeS

    MikeS Guest

    Thanks Smarty for your info,

    Sorry I meant Thyristor, god knows what I was thinking about! Also I did not
    take into account that the bracket was at ground/earth. I'll do my tests
    again. once agian thanks.
    Regards MikeS
    MikeS, May 16, 2004
  4. MikeS

    Smarty Guest


    My pleasure to help. You may also find this interesting and useful:

    Incidentally, I too am trying to get a flash to work with a new Nikon body,
    but in my case the Nikon is a Coolpix 8700. After much research, and
    eventually going to visit a couple camera shops, I discovered that most of
    the claims of compatibility of "dedicated flashes" from Vivitar, Quantaray
    and Sunpak are pure crap......... The Nikon Coolpix 8700 either does not
    fire them at all, fires them at full power thus ignoring the TTL metering /
    quench signal, or fires them once and then ignores them after they have
    recharged. I tried 3 flashguns and none of them worked right.

    Even though I am a graduate electrical engineer, the ability to learn the
    technical details has been hampered by proprietary secrecy regarding how
    each of the manufacturers supports TTL. The confusion added by D-TTL, e-TTL,
    s-TTL, and i-TTL from various vendors doesn't make it any easier.

    I eventually ordered Nikon's top flash, the SB-800 and said "enough is
    enough"!. It has an extremely high guide number and will (I presume!) work
    properly, albeit with very few of its' features functional on the Coolpix. A
    D70 body would make this flash sing, but I am not interested in another
    heavy (relatively speaking) camera.

    Good luck and let me know if I can help you further.
    Smarty, May 16, 2004
  5. MikeS

    MikeS Guest

    Thanks Smarty,
    Reading the under Cameras underwater article highlights the difficulties and
    as you say enough is enough. The manufacturers have it sewn up. Make
    relatively cheap camera and charge the earth for accessories. Highlighted in
    a letter to the Amateur photographer Magazine UK May edition.
    A reader had worked out that one litre of ink for the Epson series of photo
    printers costs £1,76412 which makes it more expensive than Channel no
    5(£52.99 for 100ml), 2300 times more expensive than UK unleaded petrol, 50%
    more expensive than the price of rare whisky like elizabeth grand old Parr
    at £800 per bottle.
    As the writer said "I don't mind paying for quality goods but ink jet inks
    must be one of the greatest rip-offs in all time" he couldn't see the
    justification for such blatant profiteering - unless of course ,its to keep
    the fat cats at major companies regularly supplied with £800 bottles of

    It looks as though I'll have to bite the bullet and fork out the dosh.
    Thanks for your help.

    MikeS, Sadder but as a compensation wiser.
    MikeS, May 17, 2004
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