Kari Kivisalo wrote:

>My assumption was that the characteristic curve
>http://www.kodak.co.uk/global/en/professional/support/techPubs/e55/f002_
>0494ac.gif is the system transfer function [scene ->
>paper/transparency].

The film used here is a slide film, so it's a transfer function
[scene->transparencey]. The filmtype, exposure and development(process 
K14) define the transfer function.

> If the transfer from film to paper/transparency is
>not linear this would have to be modelled too.

It's not linear, the dynamic range of film is bigger than that of paper. 
So you don't develop your film to the max density but to a density and 
contrast range that fits to the range of your paper (in fact to the range 
of your printing proces as the type of enlarging apparatus also matters).

Some curves of the tri-x b&w negative film, near bottom of page:
http://www.kodak.co.uk/cluster/global/en/professional/support/techPubs/f9/
f9.shtml#10

Ingo

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