[Alt-photo] Re: Stochastic screening in Gum
noisy at rogers.com
Sat Dec 7 22:11:10 UTC 2013
I've tried stochastic screened negs output on an imagesetter with varied
Things to consider: too small of a dot will not 'hold' in the
highlights; negative and paper have to be very tightly sandwiched; the
more 'point source' the light, the better; the more dense the ink (in
terms of uv blocking) the better. Also, bear in mind that most FM
screens are geared towards offset printing, which is a very different
animal than gum. There is a lot more to high-end FM screening than a
simple dither algorithm; hybrid AM/FM screens with complex error
diffusion are required to hold the highlights and avoid ugly "wormies"
(a mottled/stippled artifact).
The JPD (just-printable dot) has to be determined by trial and error;
the paper surface, sizing, and gum qualities all be significant variables.
That all being said, it can work very well, but is definitely a quite a
few steps away from "analog gum". YMMV :)
On 06/12/2013 6:21 PM, Peter Friedrichsen wrote:
> Has anyone applied a stochastic screen to gum printing? This is a half
> tone technique that uses dot frequency to emulate color/greyscale. The
> smaller the dot size, the more photographic the rendition. My UV box
> generates diffuse UV light so I think that may not be as effective as
> a more point sourced arc type UV lamp.
> Has anyone done anything like this before? I was wondering what the
> minimum dot size that could be realized from a contact negative?
> Peter Friedrichsen
> Alt-photo-process-list | altphotolist.org
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