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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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