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Voltage/Current thru shutter

 
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SYNCHROJAMES



Joined: 12 Jun 2007
Posts: 36
Location: SAN DIEGO CA

PostPosted: Sun Sep 13, 2009 4:05 am    Post subject: Voltage/Current thru shutter Reply with quote

I have an odd question-does anyone out there know what the maximum voltage/current can be sent through the contacts in the shutter? I have a 135mm optar in a Graphex shutter with x-sync only. I ask this because I was trying to come up with a way to have electric bulb/strobe flash that would mimic the 20ms burn time of a flash bulb, giving the best[I hope] of both types.
thanks
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Dan Fromm



Joined: 14 May 2001
Posts: 1892
Location: New Jersey

PostPosted: Sun Sep 13, 2009 4:30 pm    Post subject: Reply with quote

Trigger voltage and current have nothing to do with an electronic flash's burn time. "Studio" flashes have longer burn times than most portables, check the manufacturers' specs. FWIW, the longest duration portable I'm aware of is the Agfatronic 643; its burn time at full power is 1/200th, considerably faster than you want.
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glennfromwy



Joined: 29 Nov 2001
Posts: 903
Location: S.W. Wyoming

PostPosted: Sun Sep 13, 2009 10:40 pm    Post subject: Reply with quote

The contacts can generally survive 50 volts DC. It's the amperage that can weld the contacts together or burn them to a crisp. Flash bulbs draw an average of 1 1/2 amps per each, if memory serves. You could flash a half dozen bulbs with the shutter sync using 3 "D" cells, and that's pushing it. More than that would generally involve the use of a larger battery, controlled through a small relay which was tripped by the shutter and a separate small battery.
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Glenn

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SYNCHROJAMES



Joined: 12 Jun 2007
Posts: 36
Location: SAN DIEGO CA

PostPosted: Thu Nov 26, 2009 11:10 pm    Post subject: Reply with quote

I finally tested my concept for flash bulb replacement. Good news/bad news. I made a holder for a 14v bulb that popped in just like a flash bulb. It functioned fine, and with five 9v batteries in series for 45v, it put out what I thought would be adequate light. Using my recently acquired Heiland adjustable flash head set to far, a 2sec exposure at f4.7 produced a usable image slightly smaller than a quarter in the middle of a 6x7 neg. Not even close to a press 25, or even my Strobonar. Oh well, it was a fun learning experience and I still have a good stock of clear 25's. Happy Turkey day to all.
James
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glennfromwy



Joined: 29 Nov 2001
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Location: S.W. Wyoming

PostPosted: Fri Nov 27, 2009 8:15 pm    Post subject: Reply with quote

If you're only getting a small spot on the negative, I sounds to me like the flash is out of sync. If it was in sync and didn't make enough light, you would have an evenly under exposed negative. It's firing with the shutter blades only partially open. I don't think there's any way you can get electronic flash to sync the way you're doing it. It must fire at the instant the blades are fully open. It's much too fast to do that with a 20ms delay except at very slow shutter speeds. The recommended time for using elec flash with bulb synced shutters is 1/5 second or slower.
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Glenn

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pv17vv



Joined: 22 Dec 2001
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Location: The Ardennes, Belgium

PostPosted: Sat Nov 28, 2009 5:44 pm    Post subject: Reply with quote

Glenn,

Quote:
You could flash a half dozen bulbs with the shutter sync using 3 "D" cells, and that's pushing it.


How did Weegee's colleagues manage to keep-on shooting on long-duration assignments then ? Left pocket full of bulbs and right pocket full of "D" cells ?

Georges
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glennfromwy



Joined: 29 Nov 2001
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PostPosted: Sat Nov 28, 2009 8:07 pm    Post subject: Reply with quote

Georges, I think you misunderstand. Six bulbs at once, not six flashes. Two fresh D cells barely have enough power to fire six at once reliably and a setup like that would normally be confined to studio work. Using one bulb at a time the batteries will last a while. The zinc-carbon batteries of the day didn't last near as long as today's batteries, though. They did carry spares in their case.
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Glenn

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pv17vv



Joined: 22 Dec 2001
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Location: The Ardennes, Belgium

PostPosted: Sun Nov 29, 2009 5:05 pm    Post subject: Reply with quote



Thanks Glenn !
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SYNCHROJAMES



Joined: 12 Jun 2007
Posts: 36
Location: SAN DIEGO CA

PostPosted: Mon Nov 30, 2009 8:08 pm    Post subject: Reply with quote

Glenn
Actually I used the bulb setting and a 2 sec exposure-the flash synch worked fine with the rest of my test, both with bulbs and strobe.
James
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SYNCHROJAMES



Joined: 12 Jun 2007
Posts: 36
Location: SAN DIEGO CA

PostPosted: Mon Nov 30, 2009 8:14 pm    Post subject: Reply with quote

OOPS!
I forgot to mention-my lens has only the X-synch setting.
James
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glennfromwy



Joined: 29 Nov 2001
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PostPosted: Tue Dec 01, 2009 1:09 am    Post subject: Reply with quote

Ah, good. With a 2 second exposure it doesn't require much in the way of synchronization. You could actually hold the flash in your hand and set it off manually at that speed. Have fun!
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