RE: [APML] E200 star image size.

[Kirk Carbo <kcarbo@lobosservices.com>]

An increase in film speed is not the only effect of push processing.  Push
processing causes an increase in overall density, but the increase gained in
density is greater in the highlights than in the shadows.  So in addition to
increasing the speed of the film, push processing increases the contrast
gradient of the negative/slide.  A good thing for low contrast subjects like
many of the objects in the sky. 

Kirk Carbo 

>-----Original Message-----
>From: Jon Kolb [mailto:jkolb@datawest.net]
>Sent: Tuesday, November 11, 2003 7:25 AM
>To: jasonw@galaxyphoto.com; 'Discussion of Film Astrophotography'
>Subject: RE: [APML] E200 star image size.
>
>
>Jason,
>
>> Why would that make a difference? Pushing produces more 
>> density just as exposure time does. 
>
>My assumption, apparently incorrect, was that the shorter 
>exposure would
>reduce halation.  If push-processing causes the same effect, then the
>only reason to push is to shorten exposure time.
>
>Sincerely,
>Jon Kolb
>Adventures in Astrophotography
>http://home.datawest.net/jkolb/
>Life Member, International Dark-Sky Association
>jkolb@datawest.net
>
>
>
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