Re: [APML] Enhanced Sky Glow or Enhanced Film Sensitivity?

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

I have two pictures that show the effect of "chilling out" on my cold camera
page - http://members.shaw.ca/jmirtle/coldcam.htm . There are 2 shots of
M45/Mars near the top of the page. The ambient shot is about 25F, the other
at about -40F. There is about a 6x to 8x improvement in performance, BUT
only because the film was pretty lousy to begin with. The cold temperatures
slow the decay rate of the latent image during exposure, allowing a strong,
stable and well colour balanced image to form. At higher temperatures the
latent image is unstable due to the low intensity of incoming photons, and
the latent image (in the faint parts of the image) decays almost as fast as
it forms. Hypering achieves the same end result, but in a different way. As
E200 already is a pretty good film, it won't exhibit as large a performance
improvement as the 1980's Ektachrome in my example. Hence my vote for the
airglow theory, especially at 25F.

Please don't take my comments as to why cold cameras work as gospel - they
could be out to lunch. If someone has a better explanation..... Also, does
anyone understand why some films respond only to cold and others only to
hypering? Tech Pan rocks when hypered, but it isn't even good as a duct tape
replacement when cold.

John Mirtle
Calgary, Ab. Canada

----- Original Message ----- 
From: "Stuart Heggie" <stuart.j.heggie@sympatico.ca>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Friday, November 14, 2003 7:42 PM
Subject: Re: [APML] Enhanced Sky Glow or Enhanced Film Sensitivity?


I bow to John's superior knowledge of cold Canada - he's in Alberta, I'm in
Ontario - we don't get cold like he does! (but I did spend two winters in
Winnipeg and I gotta tell ya - there ain't nothin' like that - if I told the
true stories nobody but a Winnipegger would believe them)
Stuart

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