From: "Rev. Sidney Flack" <sgflack@prodigy.net>
The light readings may be different even if the cameras have identical lenses
for the simple reason they are three independent systems. Each system is
unique. One would hope the variances are limited, but they may be different.
They would also be different if they are all three set up on independent
tripods at the same time focused on the same gray card because they will must
be set up in different positions each with a different angle of reflectance.
But, if the gray card is sufficiently large to accommodate the widest lens so
that the only thing in the view finder is the card and the card is *evenly*
illuminated so that there is no change in reflectance from corner to corner and
the cameras are each set upon the same tripod in the same point of view, the
different EV readings from each system will be limited to the nuances of each
lens and meter.
However, If those are truly equal, the readings would also be equal because the
intensity of the light would be the same irrespective of focal length. As
f-stop is the ratio of aperture opening to focal length, if those ratios are
truly identical (which they are not), each lens would then pass the same volume
of light through to the film plane and meter. If the shutters are of identical
speed (which they are not), the each shutter would all pass the same volume of
light for the same amount of time. Exposures would be the same.
One way to get to that last point is to use the same body for each lens. This
would eliminate the differences in light meters and restrict variances to the
lenses themselves.
to my ears (or better yet eyes all this means that no matter what hand help light meter you use, you will not be getting the proper exposure result having set the camera at Manual....isn't it so?
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