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[Luke79]

Greetings,

ive got one question concerning the 2 Bipost Pins on my Speed Graphic
is it possible to buy a bipost to pc female adapter cable and use the speed graphic with focal plane shutter to trigger the electronic flash tru the pins?

Luke

[45PSS]

Yes a BiPost to PC adapter cord will fit the BiPost connector on the body and if the contacts are not corroded it will fire an electronic flash but you will get a very under exposed image to a blank piece of film.

There are two contact strips at the top edge of the film opening and a short strip of metal on the curtain at the lead edge of the aperture opening. As the curtain travels the flash contacts make triggering the attached flash. Flash bulbs have a 15 to 20 millisecond (.015 - .02 seconds) rise time to reach 2/3 of their peak output. Focal plane flash bulbs for up to 2x3 cameras have a burn time ( 2/3 of peak up to peak then down to 2/3 of peak [useful light output]) of 20 milliseconds and 4x5 focal plane flash bulbs have a burn time of 50 milliseconds.
http://www.donsbulbs.com/bulbs/g623/l/ge1954/09.gif
An electronic flash has a duration (equivalent of burn time) of 1/200 - 1/1000 ( .005 seconds to .001 seconds).

A .005 to .001 second burst of light .015 seconds before the aperture opening reaches the lead edge of the film will not illuminate much.

You can set the curtain to T, trip the curtain, manually fire the flash, then close the curtain and get a good flash photograph. This is called open flash.
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