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Old Apr 25, 2005, 6:28 AM   #1
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I wish to ask the way of calculation of trigger voltage from 2 external flash used at the same time , for example one for the fill-in light and one for bounced light.
For example if flash A has trigger voltage= 20 volt and flash B= 10 volt , is calculation two flash become 30 volt or there is another special formula?
Whether quantifying calculation both the lamp used in the case of maximum trigger voltage enabled by one digital camera or enough trigger voltage from one just flashlight having value of trigger biggest(Two flashes used at the same time by hotshoe-adapter that having branch of pc terminal)
We thank you for its clarification.
:-)
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Old Apr 25, 2005, 10:17 AM   #2
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bdiarto wrote:
Quote:
I wish to ask the way of calculation of trigger voltage from 2 external flash used at the same time
It's not a good idea to just connect 2 flashes with the trigger connections in parallel, if it's what you like to do, the result may be unpredictable.
Make use of accessories for that purpose (Nikon, Minolta, etc.. have these), or use a slave cell to trigger the second flash.

PS:

If you still want to connect 2 flashes by yourself, at least, use 2 diodes for safety:

flash 1, positive ------>|---------+
|
flash 1, negative -----------+ |
| |
flash 2, positive ------>|----------+-------- camera hotshoe or PC
|
flash 2, negative -----------+--------------- camera hotshoe or PC


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Old May 27, 2005, 12:11 PM   #3
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Hi

It`s not a good idea to join two flash`s together. One may have a low trigger voltage ,therefore the volts working for the capacitor may be two low for the other flash , you could blow it. it`s a simple matter to have one flash as slave to the other.
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Old Jun 12, 2005, 2:15 AM   #4
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hi,

i just bought a vivitar 2800. it won't trigger a testflash when itsin contact witha digitalmulti-meter; but the multi-meter reads a 32.1v to 40v reading every time i try to test it without triggering. i'm i doing it correctly? I want to use the flash for my kodak dx7590; kodak says that flash voltage for the camera is 500volts. i would assume that it is safe to use the vivitar on my digicam?
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Old Jun 12, 2005, 2:54 AM   #5
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Zero Interrupt wrote:
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it won't trigger a testflash when itsin contact witha digitalmulti-meter; but the multi-meter reads a 32.1v to 40v reading every time i try to test it without triggering. i'm i doing it correctly?
Yes, it is the way. The reading is meaningful if the flash is not yet triggered (not fired) but in ready state.

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I want to use the flash for my kodak dx7590; kodak says that flash voltage for the camera is 500volts. i would assume that it is safe to use the vivitar on my digicam?
Yes. 40 volts is not a low trigger voltage, but there are old flashes with more than 100 V. If Kodak confirm that, I would be confident to use it.
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Old Jun 12, 2005, 8:56 AM   #6
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thanks for the quick reply.
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Old Jun 14, 2005, 1:05 PM   #7
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FYI - Kodak pretty much confirm it here: http://www.kodak.com/global/en/servi.../tib4378.jhtml
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Old Jun 15, 2005, 8:25 PM   #8
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I had an old Vivitar flash (285) that I wanted to use with a digital camera. I was concerned about trigger voltage. BUT, there are two things to consider. One is relatively long voltage pulse that a volt meter can read. But, just as important are transient voltage spikes (high voltage for a VERY brief time that do not show up on a voltmeter). I used an oscilloscope to look for both. My Vivitar had a trigger voltage under 12 volts, EXCEPT, every now and then, a greater than 50 volt spike appeared!

So, I bought a Wein hot shoe - hot shoe volt spike protector (about $50) and mount the adaptor onto the camera's hot shoe and the flash onto the adaptor.

This may be overkill, but at least I know the camera is protected from the trigger voltage and spikes.

Hope this helps,

Bob


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