Warren wrote :
> snip...
> I've sort of observed the same thing. Maybe the diode that shines into
the
> silicon cell to cut off exposure at 2-4 minutes also acts to decrease
> exposure times for very low light intensity levels.
>
Ever heard of reciprocity failure? In a nutshell, at long exposures
(typically more than 1 sec), a reduction of 1 f-stop in aperture is not
equal to a doubling of exposure time - one will have to give much longer
exposure.
For example, an metered exposure of 2 secs at f16, may actually require 4
secs at f16. Not a problem with the camera or meter, just the sensitivity
(exposure) response of the film. Typically most short exposure (regular
daylight) film is accurate at its rated ISO speed only in the range of
about 1/10 to 1/4000 sec exposure time. Long exposure film (usually
specially designated, and typically type B) has the correct exposure slope
for exposures of 10 sec to 1/10 sec.
Regards,
Richard
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