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  1. #1
    Edimilson's Avatar
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    New Vivitar 285HV suitable for Canon Rebel T2 and Bessa R3A?

    Hello all!

    Sorry in advance for this newbie question!

    I own a Canon Rebel T2 (also known as EOS 300V) as well as a Voigtländer Bessa R3A. I have decided to buy a flash unit and have come across the Vivitar 285 HV. I have done some research at APUG and elsewhere and people seem to agree that it's a good choice considering its price.

    Problem is: after being around for decades, the new Vivitar 285 HV is now being produced in such a way as to be fit for modern digital cameras. This has to do with volts and electricity, a field in which my ignorance is boundless. I quote (http://www.popphoto.com/lighting/398...-review.html):

    "The biggest change to the latest incarnation -- and the reason for reintroducing it -- is the sync voltage: Many modern DSLRs and advanced compact digitals sync up with external flash units using six volts or less in the sync circuit. Unknowing 35mm film converts, upon switching to digital, have hooked their old reliable flashes up to their new cameras only to find the sync circuits fried quickly. The older Vivitar 285 and 283 both had sync voltages between 200 and 260 volts, high enough to give modern six-volt circuits a heart attack. The new 285HV model syncs at under six volts, perfectly safe for today's digital cameras."

    My question is: would the new Vivitar 285HV be adequate for use with my film cameras?

    Thanks!
    Edimilson

  2. #2

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    Absolutely. The Rebel T2 is like digital cameras, it can't handle flash sync voltages that are very high. At least my Rebel 2000 couldn't.

    I have a Vivitar 283 I got from Goodwill for a few bucks about 6 months ago, and it's a great flash. I'm sure the 285hv is no exception.

  3. #3
    Edimilson's Avatar
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    Thank you, Brofkand. I understand the new model would work just fine with the Rebel then. But what about the Bessa R3A? Any thoughts?

  4. #4
    eric's Avatar
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    I'm not sure about the 285's but I have an army of 283's. I don't chance it on my Xti. I got a Wein safe sync.

  5. #5
    Steve Smith's Avatar
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    Whilst the newer 285 HV does have a lower sync. voltage, the HV designation has nothing to do with this. It actually stands for High Voltage and refers to the high voltage connector (for a separate power supply).

    Of the older 285s, some were high voltage. According to this website: http://www.aljacobs.com/ultimate_vivitar_285hv_page.htm

    The flashes marked 'made in Japan' are high voltage whereas the rest are low.


    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.

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    Edimilson's Avatar
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    I'm sure now the Vivitar 285HV I bought will suit my Bessa. I've already acquired a Vivivtar 2800 for my older film cameras. Thank you all.

  7. #7
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    Quote Originally Posted by Edimilson View Post
    I'm sure now the Vivitar 285HV I bought will suit my Bessa. I've already acquired a Vivivtar 2800 for my older film cameras. Thank you all.
    If you own a volt meter you can measure the d.c. voltage accross the contacts. My old 285 reads about 7.5 VDC and I've used it safetly on DSLRs. However it's best to measure what your own unit charges to or use the Wein Saftey sync for suspected/unsafe high voltage units - cheap insurance.
    Don Bryant

  8. #8
    tim_walls's Avatar
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    Quote Originally Posted by Edimilson View Post
    Thank you, Brofkand. I understand the new model would work just fine with the Rebel then. But what about the Bessa R3A? Any thoughts?
    Should work fine.


    For an understanding of the problem:

    The standard flash sync connection is just a switch. The outside of the hotshoe and the pin the middle are connected together when the shutter is open, and open when the shutter is closed.

    On many cameras - any all-mechanical camera, like an old 35mm or a brand new LF shutter - this is just a simple mechanical mechanism; two contacts that come together when the shutter is opened.

    On 'simple' flashes, in very simplistic terms you can think of the recharging circuit as being a battery connected to a capacitor which charges the cap up to a nice high voltage - e.g. 250 volts. The capacitor is also connected through a switch to the flash gun; close the switch, and the capacitor discharges all its stored energy through the flash gun in an instant.

    The problem with old flashes is the 'switch' is just the hotshoe. I.e. one of the high-voltage outputs of the capacitor is connected directly to the centre pin, and the flash bulb is connected directly to the outside of the hotshoe. When the shutter connects the two together, the capacitor discharges (through the centre pin, via the shutter, back to the hotshoe and into the flash bulb.)


    This all works fine. It even works fine with electronic cameras that use a Thyristor to replace the mechanical switch with an electronic switch (I believe high-end professional electronic cameras probably still use thyristor switching.) Thyristors can handle large voltage/current switching easily.

    The trouble with thyristors is principally that they are physically quite large, which obviously doesn't fit with the miniaturise-everything approach of camera manufacturers. So many modern consumer level cameras use a transistor instead. Except, of course, stick 250 volts through a small transistor and the thing will probably blow up. (In a sad, life expiring fizzle kind of way, so don't try and replace your fireworks display with this.)

    The solution is to move the thyristor into the flashgun - so you present only the low battery voltage through the hotshoe, and instead of hooking the hotshoe directly up to the capacitor/flash, you connect it to a thyristor in the flashgun which then connects the capacitor to the flashbulb.



    So, to cut a long story short:
    Old flashguns with high-voltage hotshoe - work fine on old cameras, should be on professional new cameras but check, will blow the switching transistor on modern compact cameras.

    New flashguns with low-voltage hotshoe - work fine on any camera.



    Edit: Just for the pedants/curious, I missed one component out of my 'simple flashgun' circuit, which is the inverter which uprates the DC battery power to the 250V to charge the capacitor - this is just a simple oscillator & transformer circuit, and it's this bit that creates the whining noise as the flash charges.

    You can actually still buy brand-new flash units that still operate this way - I have three dead-cheap (10 buck type cheap) fixed-output flash units bought new last year which forgo a thyristor inside.

    A Wein Safesync type device, incidentally, is simply a thyristor inside a small box :-).
    Last edited by tim_walls; 01-11-2009 at 06:49 AM. Click to view previous post history. Reason: Added pedantry :-)
    Another day goes under; a little bourbon will take the strain...

  9. #9
    DBP
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    The only issue I can see would be the size of the Vivitar on the Bessa. I use a cheap little Sunpak 1600A for better balance.

  10. #10
    Edimilson's Avatar
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    Thank you Donbg, it's good to know I may use the new Vivitar with older cameras. The degree of control you can have on the 285 as compared to the 2800 is certainly going to be useful.

    And DBP, this is a good point. I didn't know the 285 was so great because I had only seen pictures of it on the internet. But some days ago I had one in my hands at a store and it's really quite big. I'll have a look at the Sunpak model you mentioned. Thanks.

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