[pure-silver] Re: Polycontrast Paper Performance / Cold lite

----- Original Message ----- 
From: "DarkroomMagic" <info@xxxxxxxxxxxxxxxx>
To: "PureSilverNew" <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, October 18, 2004 10:36 AM
Subject: [pure-silver] Re: Polycontrast Paper Performance / 
Cold lite


> My one-time experience with Selectol Soft brought paper 
> contrast down by
> less than 1/2 grade. Since I get similar or better results 
> with changing the
> factor of factorial development (FB papers only, of 
> course), I gave up on
> soft developers and the increased darkroom complexity they 
> bring.
>
>
>
>
>
> Regards
>
>
>
> Ralph W. Lambrecht
>
>
   I am puzzled by how the developer can affect paper 
contrast at all. Prints are developed to "completion", that 
is to the highest contrast the material is capable of. 
Negative film is not developed to completion but rather to 
some desired contrast. Paper contrast would also vary 
somewhat if developed less but the main difference would be 
a loss of density in the shadows. What experimental data 
shows is that once exposure and development are sufficient 
to obtain full black from the paper that variation in 
development time simply moves the characteristic curve 
horizontally along the graph but does not change its slope 
significantly. Of course, this varies with the paper. A "low 
contrast" developer like Selectol-Soft or Agfa 120 develops 
more slowly than a more active developer like Dektol, but, 
unless there is some selection of grains by the developer, 
the contrast should be the same provided the same shadow 
density is reached.
   Perhaps there is something here I don't understand, if so 
I would certainly like to. My understanding is that the 
contrast of paper is determined mainly by the distribution 
of sensitivity of the silver halide particles in the 
emulsion.
   I will define contrast as I understand it as being the 
range of difference of exposure that results in a given 
range of density in the image. In a print that density range 
is from paper white to the maximum black the material is 
capable of.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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