Re: [OM] Re: XA flash shoe

Subject: Re: [OM] Re: XA flash shoe
From: "C.H.Ling" <chling@xxxxxxxxxxxx>
Date: Fri, 10 Nov 2000 09:04:57 +0800
You are also partially correct, the T32 is from 1/1000s to 1/50,000s
(max power to min power), while the old Metz T45 at max power output
was only 1/300s. 


clintonr@xxxxxxxxxxxxxxxx wrote:
> You're partially correct - a CdS cell cannot react to light from a
> strobe.  Even changing the intensity of light two or three "stops" will
> take several seconds to reach full impact on a CdS cell - and the
> typical maximum duration of a strobe is in the neighborhood of
> 1/10,000th second, often faster.
> One correction on the XA's function, however - they actually use two CdS
> cells, one of which controls only the meter needle in the finder, the
> other being connected to the circuit that controlls the exposure.  There
> is no "memory" function - in other words, the exposure isn't "set" when
> the release button is pressed, it is judged in real time.  The exposure
> control circuit keeps the shutter's electro-magnet energized (keeping
> the shutter blades opening/open) until it registers that enough light
> has struck the CdS cell to provide a proper exposure - then it
> de-energizes the electro-magnet, allowing the blades to begin closing.
> The exposure during this closing time is included in the exposure
> calculation.

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