Re: [APML] Reciprocity of older films

["Don Westergren" <westergren@netzero.net>]

Brian,

I don't think you can compensate for exposure on nebulas and galaxies, shoot
as long as you can without getting sky fog.  The main thing that happens to
color film due to age is a change in color balance.  That is the reason for
the expiration date on both consumer and pro films.  The color balance of
consumer films is set to be best about mid way through the life of the film.
Pro films start out near "perfect" color balance and must be stored cool to
keep a reasonable (and tight or non changing) color balance until
expiration.  Cool or Cold storage slows the color change.  There's a debate
whether to freeze or not freeze for best results.  Kodak recommends both in
different papers.  The other long term effect on film is the little spots
that will show up due to cosmic ray hits.  The older the film, the more
cosmic rays pass through.  Cosmic rays go right through refrigerators and
freezers.

My film tests did not try to distinguish changes in reciprocity due to age
on regular films.  I did see an increase in long exposure response for
hypered PPF400 and PJ400 at 4 months and 22 months in a freezer.  Most of my
film tests were done in the summer of 2002.  My testing of films like PPF400
and PJ400 were on out of date film at that time, yet they performed very
well.

The PPF400 needs hypering to perform best, and is much better 4 months after
hypering.  Supra400 doesn't need any hypering.

Don


> Hi all,
> Does reciprocity of film change as it gets older?
> The reason Im asking is I met up with an apml'r today
> who gave me some ppf and supra 400 which was well
> taken care of.
>
> Im not sure the date on the film but i think its like
> "99" or "98".
>
> Do I have to compensate for exposure considering its
> age?
>
> Thanks,
> Brian
>
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