Archived posting to the Leica Users Group, 2001/10/03

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Subject: RE: [Leica] Xtol newbie
From: "Lee, Jonathan" <Jonathan.Lee@hrcc.on.ca>
Date: Wed, 3 Oct 2001 10:30:57 -0400

But more to the point, can someone actually show or tell me what
advantage Xtol 1:3 has over a 1:1 dilution?

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The basic principle of high dilution and/or decreased agitation is to
preserve as much highlight information  consistent with getting as much
shadow information as possible.  Because highlights have to have more silver
deposited on the film than shadows, highlights "use up" the activity of the
developer faster than the shadows.  If you have a lot of developer or
agitate a lot, there will always be enough developer for the most dense
highlights.  Having a highly dilute developer or agitating very little means
that the developer in the highlights exhausts itself more rapidly than the
developer in the shadows.  Therefore the effective film speed of the
highlights is lower, preserving highlight information.  

Jonathan Lee
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