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Re: [OM] Re: film pushing

Subject: Re: [OM] Re: film pushing
From: Lars Haven <lhaven@xxxxxxxxxxxxx>
Date: Fri, 09 Jan 1998 22:09:03 +0100
Marco wrote:
> 
> 
> This method is (was?)  used widely in graphical arts cameras. It allows a
> finer control of the halftone %. Of course you can pre-veil the film after
> exposure, just before developing. Try for few seconds with an amber or
> yellow-green lamp (commonly used in darkrooms).
> 
> Marco
> 
This is totally off topic, but I used to work in the reprographic camera
buisness...

I think the correct verb is was, when the subject is graphical cameras.
At least the market for new ones seemed to collapse about five years ago.
Now everybody wants digital scanners. The quality suffers (at least used to),
but it is hi-tech. Sigh! I fear our treasured OM cameras may become the
victims of a similar trend in "normal" photography.

The diffuse light is, as you say, used for halftone dot ontrol, but
that exposure is normally performed with a raster screen between the 
light and the lith-film, providing control of the shadow dot %. The point
is not directly to change the sensitivity of the film, but to introduce
what is basically a controlled amount of flare. The full story of tone
control with graphic films and rasters is quite complex, involving
up to three different exposures. I will not go into that now.

Regards
Lars

-- 
Lars Haven  <lhaven@xxxxxxxxxxxxx> aka <lhaven@xxxxxxxxxxxx>
"You just predict the worst you can imagine.
 Inevitably someone is going to hail you as a prophet."
                                                Tom Leherer

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