Re: [APML] Push Processing (was Scanning slides)

[Alan Voetsch <alanv12952@yahoo.com>]

Hey Don,

Wow, thanks for the tons of info. I infer that it would NOT be a
mistake to fully expose any film. I plan to try some more E-200 and
expose the crap out of it, also I think I saw some Fuji Super HQ200 at
Bi-Mart for $2.50 a roll. Gonna try some just to see what it looks
like. I have shot nothing but Supra for 4 years now and it's sort of
fun to try something else. Yeah, don't worry, I get out plenty enough.
8-)

I do have one question regarding your comments below. You say that your
tests indicate that +2 nets a +1 for AP purposes. If I was to ask for a
push with my film, does that mean I need to ask for a +2 to get a +1?
Or that it doesn't matter

Thanks,
Alan

--- Don Westergren <westergren@netzero.net> wrote: 
> Push processing gains light sensitivity but also increases contrast
> and
> grain size for just about all films (I don't know of any films that
> don't
> fit this).  So deciding whether or how much to push process is a
> compromise.
> Slide films like E200 and Provia400 are easily push processed with
> the E-6
> chemistry and the push+1 and +2 processes are well established. 
> However,
> the push +1 and +2 was established for normal film use, with short
> exposures
> of daylight (or flash) subjects.  My exposure tests of both these
> films
> processed for +2 show that for astrophotography long exposures, the
> result
> is an honest +1 light sensitivity increase.
> 
> Contrast increase with slide films is a concern because slide films
> are
> already high contrast with standard processing, compared to color
> negative
> films.  This is why color negatives can produce a nice print even
> with under
> exposed or over exposed pictures.  Slides have a much narrower range
> of
> acceptable exposures for good pictures.  This is called the
> "latitude" of
> the film.  This may explain some of your slide scanning problems,
> since most
> of your scanning experience has been with negative films.  To get a
> good
> astro picture with slide film, you have to expose long enough to get
> an
> image of the deep sky object without a  light sky background.  For
> slide
> film in particular, you also have to avoid "sky fog" where the
> background
> sky shows up as gray rather than black in the picture.  You should
> expose
> slide film at various times to find where the sky fog limit is for
> your
> film, equipment and sky darkness, then always expose shorter to avoid
> sky
> fog.  Slide film exposed this way will scan easier.  Slide film that
> is
> underexposed is difficult to scan, as you are finding out.
> 
> May you have Clear, Dark Skies,
> Don
> 
> >
> > Most likely it would  be an improper scan and I plan to post a
> question
> > regarding that ASAP. I have always had my film developed by the
> > recommeneded process, C-41 for Supra, E-6 (?) for the one roll of
> E200
> > I've done. John's comment indicated that push processing wouldn't
> be
> > needed unless it would help get the hump of the histogram fully
> into
> > the box. Is pushing a good idea?
> >
> > Alan
> 
> 
> 
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=====
SCT Astrophotography: http://www.pbase.com/avoetsch/astrophotography
FS-102 G-11/Gemini: http://www.pbase.com/avoetsch12952/tak_fs102
& http://www.pbase.com/avoetsch12952/fs102


		
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