Re: cold temperature reciprocity

Pinhole Blender wrote:
> > From: "Earl and Patty Johnson" <earlj@comcast.net>
> > I was showing my pinhole cameras and pictures to a friend
> > recently. To my surprise, he is interested in astronomical
> > photography. In the course of our discussion, he told me that cold
> > temperatures reduce the reciprocity failure effect on photographic
> > film. He said that astronomers sometimes freeze their cameras and
> > film before an exposure to reduce the exposure time. It is a
> > little early to think about pinholing in the snow, but I wonder if
> > my friend is correct, and how cold does it have to be to make a
> > difference?

Cold cameras were used in the 1970s. Besides getting the film cold
you also needed to get rid of the humidity. Purging the camera with
Nitrogen was one way do this. Testing by Michael Covington showed
that most people were running their cameras too cold.

> I don't know about freezing but a friend of mine used to pressure
> cook his film in a chamber of hydrogen which gave him very extended
> ISO for no increase in grain. He had a grant to shoot in Antarctica
> during their winters with only star light.

Gas hypering isn't as popular (or useful) as it used to be. As film
technology has changed these tricks have become less and less useful.
For example, Kodak's E200 has such a low reciprocity failure that gas
hypering it isn't worth the trouble. Tech Pan still benefits from gas
hypering, but unfortunately Kodak has announced that Tech Pan is being
discontinued.

-- 
Brian Reynolds                  | "But in the new approach, as you know,
reynolds@panix.com              |  the important thing is to understand 
http://www.panix.com/~reynolds/ |  what you're doing rather than to get
NAR# 54438                      |  the right answer." -- Tom Lehrer
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