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Re: [APML] Portra 800? was: 4x5 color negative
Hi Fred:
That is interesting! My test shots with Supra 800 were done last year, so
it's possible that the film had changed in the interval between yours and
mine. Or, maybe your processing was able to remove the cyan <G>? But I think
you would have mentioned it if it had been as bad as mine
http://www.astronomy-images.com/Tests/test-of-kodak-Supra800-film.htm . Not
subtle at all!
Anyway, I await further developments (pun) with interest, although I don't
intend to try Supra 800 again. Is it still available in Canada? I think it
has been withdrawn in the US, along with Supra 400. Of course, it may be
just renamed to Portra 800 as Don Westergren suspects.
Best of luck with your imaging,
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: Thursday, April 24, 2003 3:59 AM
Subject: Re: [APML] Portra 800? was: 4x5 color negative
Hi Bert,
the shot was taken now more than 2 years ago when i think, Kodak Supra was a
newcomer on the market ( correct me if i'm wrong ). The film was a fresh
roll. The store where i've purchased the film always keep film on
refrigerator ( slightly better than at room temperature ). I can still have
Supra 800 at this store if i'm right. I've planned to retry this film on the
pleiades because i've got surprising results on this object with Supra (
http://www.quebec-astro.com/Les_Pleiades.htm ). To be honest, this was the
only objects with good results ( M42 and M45 ). Other such as M33 for
exemple, was ugly with an awesome green color shift. As you say, if Kodak
has improved the film ( as if improvements have something to do with better
results for us ! ), it's near 100% sure that the Supra 800 is not the same
i've used ( in spectral response ). One of the best exemple is the successor
of the former Fuji Superia - the Fuji X-TRA. When Fuji has "improved" this
film, the red sensibility was lost for us. But the X-TRA is an excellent
film for galaxies with no red nebulae. Here an exemple of NGC891 taken with
X-TRA ( http://www.quebec-astro.com/NGC891.htm ). So, if i try the Supra
again Bert, i'll let you know about the results.
About the processing, yes i've done processing. But surprisingly, not a lot
was done. Just to remove the subtle green recorded.
We keep in touch.
Regards,
Frédéric Caron
Québec, Canada
----- Original Message -----
From: "Bert Katzung" <katzung1@attbi.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, April 23, 2003 11:50 PM
Subject: Re: [APML] Portra 800? was: 4x5 color negative
> 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
> > >
> > >
> > > _______________________________________________
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> >
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> >
>
>
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