Re: [APML] Copygraph finished and hypering Q

["John C. Mirtle" <jmirtle@shaw.ca>]

Kent,
    All I can call upon is 17 years of practical experience in shooting
hypered and unhypered films at focal ratios ranging between f 4.5 and f11. I
have never, ever seen a decrease needed in exposure time when shooting
snapshots just because film has been hypered. (moon, planets, sun, etc) My
understanding is that films' speed is mostly determined by it's chemical
make-up, shape and size of the film grains and a number of other physical
properties. Tech pan's speed is different in that it is also controllable by
the choice of developer. Low intensity reciprocity failure IS changed in
some (but not all) films by gas hypering, but the speed of the film is still
determined by it's physical properties. In practice a moon shot on tech pan
of 1/1000 of a second will produce the same image as a 1/1000 second shot on
hypered tech pan, if development remains constant. (above base fog) A W92
filtered shot at f1.5 for 45 minutes will be radically different, which is
why we hyper.
    Gas hypering is only one method of reducing reciprocity failure.
Chilling film to -40 improves the performance of some films  to long
exposures as the decay rate of the latent image is slowed sufficiently for a
good image to form under faint light. Interestingly, at -40 film takes
longer to form an image when exposed to short exposures! So, for this type
of hypering you must expose LONGER than you would for normal (warm) film for
short exposures.
    Brian wanted to know if exposure compensation was needed for hypered vs.
unhypered tech pan for exposures of the moon at f4.5. I still stand by my
statement of "no" for exposure times of a few seconds or less. If it was
being shot through a pinhole camera and a welders glass the answer would be
yes. Reducing low intensity reciprocity is the purpose of hypering. Changing
effective ASA rating is a function of the developer and the chemists at
Kodak - not of hypering. Try it. :-)

John Mirtle
Calgary, Ab. Canada

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John:
Sorry, but you are incorrect about hypered Technical Pan film.
The speed of Tech Pan varies with the type of developer used and the length
of development. In a fine grain developer like Technidol it's speed is rated
as 16 but in Dektol it is about 200.

Now, when you introduce hypering, it's speed increases to over 250 (in D-19
undiluted) and it's reciprocity is dramatically reduced.

Kent Kirkley

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