Hi all,
to see my Orion nebula taken with Supra 800, go there :
http://www.quebec-astro.com/La_Nebuleuse_dOrion.htm
Fred
----- Original Message -----
From: "westergren" <westergren@netzero.net>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, April 23, 2003 1:26 PM
Subject: Re: [APML] Portra 800? was: 4x5 color negative
Bert,
Pat Freeman and I both tested Supra800 with the same conclusion: it has
extremely low red sensitivity. I also tested Portra800, and the result is
the same as Supra800. My guess is that they are both the same emulsion. I
don't use either for AP.
Don
Hi Jerry and all:
I've been haranguing about Portra 800 and Supra 800 for some time now
because they are awful for astro work. Not because of spectral
sensitivity
curves but because those curves are strictly for daylight exposure
times.
The cyan layer shows reciprocity failure much sooner than the other
layers
and being a negative film, we end up with a very cyan positive. See
http://www.astronomy-images.com/Tests/test-of-kodak-Supra800-film.htm
for the Supra result. I can't remember whether it was Pat Freeman or Don
Westergren who tested Portra 800 but the result was the same. I think
it's
time to put Supra 800 and Portra 800 behind us.
The bottom line is (as usual): the spectral sensitivity curve data have
to
be tested out at long exposure times. As given by the manufacturer,
those
curves are only the first step.
By-the-way: the book is great!
Bert
_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo
_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo