Re: [APML] Portra 800? was: 4x5 color negative

["Bert Katzung" <katzung1@attbi.com>]

Hi Fred (and Craig):
That's a wonderful image, with no sign of the cyan cast that I got with my
M42 shot. When was it taken? Could it be that your film had a different date
of manufacture? Unfortunately (?), I don't have any more of the 800 film
that I used, so I don't know the date on mine, but Kodak is famous for
"improving" their emulsions and it may be that yours was manufactured before
the "improvement." Have you taken any more shots with Supra 800 using
recently purchased film?
Alternatively, you may have processed your shot very differently. My test
shot was essentially a raw scan with just some stretching and no color
adjustment.
Thanks for any additional information.....
Bert

Bert Katzung
katzung1@attbi.com
www.astronomy-images.com


----- Original Message -----
From: "frédéric caron" <astronome@videotron.ca>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, April 23, 2003 2:27 PM
Subject: Re: [APML] Portra 800? was: 4x5 color negative


> 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
>
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