Re: [APML] stacking & adding film images

["Stuart Heggie" <stuart.j.heggie@sympatico.ca>]

Don, your comment is consistent with all that I have read about the
wider range of colour print films vs slide films. Interesting stuff!
Thanks!

Stuart
http://www3.sympatico.ca/stuart.j.heggie/Stuart.J.Heggie/
Flesherton, Ontario, Canada

----- Original Message -----
From: "Don Westergren" <westergren@netzero.net>
To: <twade@bmi.net>; "Discussion of Film Astrophotography"
<astro-photo@seds.org>
Sent: Monday, March 29, 2004 6:31 PM
Subject: Re: [APML] stacking & adding film images


> Wade and all,
>
> The reciprocity losses for E200 occur in the first hour of exposure
(for
> standard processing).  You can see the effects out to 273 minutes
exposure
> at my website:
> http://home.nethere.net/mpd/FilmTestData/KodakE200.htm.
> Beyond 1 hour, the E200 responds nearly linear to increased exposure
time.
>
> I don't have the equipment to measure the precise sensitivities of
slide vs.
> color neg film.  I have found that shooting slide film with an f5
scope
> catches a lot of sky fog after one hour at a reasonable dark site
(Laguna
> Mountain, east of San Diego).  I can easily shoot twice as long with
Supra
> 400 negative film without sky fog at the same site.  The slide film
(Provia
> 400) seems to pick up more dim nebula in one hour than a two hour shot
with
> Supra 400.  For objects with a large brightness ratio (like galaxy
cores,
> the Trapezium, etc) the Supra picks up a wider range of brightness in
a
> single exposure.
>
> Don
>
>
> > One more thing to consider is the possibility that exposing E200
beyond 1
> > hour makes very little difference due to the film's reciprocity
failure.
> > At some point, the film just can't record any more "photons"; hence,
it
> > may never make it to a very dark skies' limiting magnitude before
> > quiting; whereas, a CCD easily can achieve this given enough
exposure
> > and/or stacking.
> >
> > Wade
>
>
>
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