John Hermanson wrote:
>Yes, and which camera body is then "correct"?
They would all be "correct". The purpose of the test was to determine the
correct ASA/ISO setting to give neutral results with that body. Load a roll
of your favorite slide film and take pictures of a familiar object. A Kodak
or McBeth color chart would probably provide the most objective results, but
is by no means a necessity. Vary each exposure by changing the ASA/ISO
setting on the camera (yes, you could also just dial in + and - exposure
compensation). Make sure you keep very accurate records as to which frame
number was exposed at which ASA/ISO. When the film is developed, carefully
check the slides to determine which one represents the object correctly.
That is the ASA/ISO setting that you should always use for THAT particular
film in THAT particular camera. The test will need to be repeated for each
camera body you own. A pain, yes, but each body can vary. If you're fussy
about correct exposure with slide film, it would seem to be a necessary test
to perform. I don't have the book in front of me, but if I recall correctly,
it was necessary for John Shaw to rate Velvia at 32, 40, 50, and 80,
depending on which N*k*n F4 camera body he used. These four different
settings would all produce exactly the same results. The differences were in
the camera metering systems. As you pointed out, plus and minus 1/2 stop is
acceptable accuracy from a repair standpoint. And I imagine that other
repair persons might not be as meticulous as you are and the differences
could be even greater. Testing will solve this whole problem.
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