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Re: [OM] Will this flash set up work?

Subject: Re: [OM] Will this flash set up work?
From: "Tom A. Trottier" <TomATrottier@xxxxxxxx>
Date: Sun, 4 Feb 2001 00:46:36 -0500
Dear Hans,

I don't know how the f280 can be quenched OTF in FP mode, above 
1/60th with half the frame still to come.

Tom

On 3 Feb 2001, at 20:01, sayeth Hans van Veluwen <olympus@xxxxxxxxxxxxxxx> 

> : Hans ............. is this to imply that the F280 takes daylight into
> : account as a continuing source of light and opposed to it [the F280]
> : reacting to the intensity of the daylight at the instant it [the F280]
> : fires? If the former I can understand that the sudden impulse of light
> : from the Vivitar might cause a problem but if the latter surely isn't
> : the impulse of light from the Vivitar's flash just another source of
> : directional light the F280 has to account for when "doing its thing"?
> 
> Well compare the situation with a multi flash setup with all T flashes 
> connected
> with T cords and a body which supports OTF flash. This works because the
> combined flash output + available light (when applicable) is measured, and 
> when
> enough light has reached the film all flashes are quenched simultaneously.
> 
> In the case of one dedicated OTF flash and one none dedicated slave unit the
> F280 will be quenched when enough light has reached the film but the slave 
> unit
> will not. So if the F280 is quenched after 1/40.000 sec and the Vivitar does a
> full dump at, say, 1/1000 the picture can be (and probably will be) 
> overexposed.
> 
> The difference with OTF measuring of flash output and daylight is that the
> influence of daylight is measured from the beginning the first curtain starts 
> to
> move. First it is measured from the curtain, then from the film. When the 
> first
> curtain is 'arrived' and the intensity of the daylight allowed a shutter speed
> of 1/60 or longer the flash(es) fire(s) and its (theirs) output is added to 
> the
> light already measured; when enough light has reached the film the flash(es) 
> is
> (are) quenched. Except any non-dedicated flash that will ruin the carefully
> built-up OTF metering...
> 
> 
> hnz
> 
> 
> 
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