Re: [APML] To freeze, or not (Was: The good Supra 400 pricereduction...)

[Philip Perkins <philip@astrocruise.com>]

 From what I have seen the effects of outdated film are indeed increased 
fog - chemical fog, and less sensitivity to emission spectra.  The OIII 
response seems to go first, followed by the Ha response, and what Ha 
response remains records as a muddy brown colour.  Stars still record, but 
stars are broadband points of light and so could be expected to "punch 
through" mild fogging.

I am not so sure about fogging due to cosmic rays - we know that CCD 
detectors record them but do we know for certain that film records 
them?  Still, so little in known about cosmic rays, but since their 
appearance on CCD detectors is so characteristic, one might expect 
something analogous on film, even if only a "blob" or fuzzy streak of mild 
fogging, but I don't think any evidence has been seen has it?  I don't 
think the broad fogging that occurs across an entire film (due to aging) 
can be attributed to cosmic rays can it?  Isn't that far more likely to be 
due to chemical fog?

--Philip

At 14:28 08/05/03 -0700, you wrote:
>Alan, I have yet to see a cosmic ray hit show up on my old film when
>developed.  With a CCD you have a definite streak or dot.  Film may simply
>just fog up.  Kodak adds water to film to increase the reciprocity failure
>to keep it from self exposing in the cartridge while on the shelf from
>THERMAL energy.  Apparently the molecules bouncing about will expose the
>film grains.  In the freezer, this of course is greatly slowed to the
>point film can last 10  years or more.  Some food for thought.
>
>Chris Schur


Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com

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