Paul, I think you might be misunderstanding reciprocity failure.
At some point, the film's response to light goes non linear.
Effectively, what happens is that at (example only) a one minute
exposure, your 100 speed film is still a 100 speed film, but at
a 5 minute exposure, it is suddenly a 25 speed film. No meter
can account for that, because it is an individual film
characteristic.
William Robb
----- Original Message -----
From: "PAUL STENQUIST" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, January 06, 2001 7:44 AM
Subject: Re: Vs: Macro Metering & Exposure Compensation
> A TTL light meter will correct for any exposure variation that
involves
> loss of light through the lens and shutter, including
reciprocity
> failure. (Or perhaps I should say that since a TTL meter
measures the
> light reaching the film/sensors inside the camera, it goes to
follow
> that it does not have the same problems with long and short
exposures
> that a meter measuring ambient light encounters.) Compare the
readings
> of your TTL meter to a handheld meter for an exposure of ten
seconds or
> so, and you'll see exactly what I mean. The ability to correct
for
> reciprocity and extensions was one of the principle benefits
of SLR/TTL
> cameras. And it is a huge benefits with a camera like the LX
that will
> measure very low levels of light. No heacache invoking
calculations
> necessary for those two minute exposures.
> Paul
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