Toby Vann wrote:
> I was reading in Dan Burkholder's book
>on making digital negatives about a program called Icefields. Other
>than him and the website I have no visual or oral proof that it's really
>that good.
I have been using Icefields to output negatives on an imagesetter for
contact printing in UltraStable pigment transfer and some platinum for the
past two years. The results are excellent at 1800 dpi on Agfa Avantra
imagesetters that are well serviced (i.e. laser well focused, no dust on
the mirror, and film d-max and film processor well calibrated together.)
While Dan's method gives a slightly smoother rendering for some tones, I
find that Icefields gives the best rendering of sharp, fine detail combined
with great tonal transitions in smooth gradients like skies. If you are
outputting more than one plate, Icefields negatives are carefully
constructed to place dots from different plates contiguous to each other,
as opposed to the dots from different plates falling more randomly on top
of each other. This not only helps to represent smoother tones, even in
highlights, which is stochastic screening's weakest point, but it also
gives much greater color purity and a larger overall color gamut. I
believe that RIT studied Icefields screening and found that when used in
normal offset platemaking and printing, it produced colors which were
thought to be out of gamut, or impossible to acheive with that process. I
also compared it with Agfa's Crystal Raster screening, as well all of the
other commercial stochastic screening programs, and found it superior in
all ways.
Another benefit of Icefields is its ability to image larger pictures than
by using Photohop's diffusion dithering method. Icefields files may still
be limited by the RIP on the imagesetter that you output on, however. At
present I image at 1800 dpi and output on an Agfa Avantra for sizes up to
about 20x24. I presently output images at 1200 dpi (at an imagesetter
device resolution of 2400 dpi) for cmyk images of about 25x32 up to 30x40.
The dots at 1800 dpi are 14 microns, or about half the diameter of human
hair. Even 1200 dpi dots (at 21 microns) are invisible on watercolor
paper, or especially if you are outputting an image in duotone, tritone or
cmyk/quadtone.
Finally, Icefields has great ICC Colorsync implementation and a unique
Quadtone plug-in for duo-tone to quad-tone effects. I haven't yet had time
to explore this part of the program, however.
Tod Gangler
Seattle, WA
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