Re: [APML] Copygraph finished and hypering Q

[KGKIRKLEY@aol.com]

In a message dated 3/11/03 7:59:22 PM, jmirtle@shaw.ca writes:

>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

John:
I think we're comparing apples to oranges.
Perhaps I should have questioned why he was wanting to use hypered Tech Pan 
to photograph the moon, because it is a waste of good hypered Tech Pan. You 
are probably correct that for short exposures (like 1/1000 to 1 sec.) and 
bright light the speed isn't effected by hypering. However, for it's usual 
application in astrophotography; ie. nebulae, galaxies, etc. with HA filters, 
long exposures (like minutes to hours), hypered Tech Pan does have an 
increased exposure index over unhypered Tech Pan.  

Kent Kirkley
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