Date: 11/09/01-03:34:51 PM Z
what you say makes sense. Since digital images are limited to 256 shades , a
step wedge that includes 256 levels is going to have a posterized effect.
There is no way to get around this. But you can do a couple of things to
minimize the apparent effect.
1. If you are using a gradient in an image (adding it in), limit the length
of the gradient so that the bands are very thin and thus lest noticeble.
2. Use Gaussian Blur slightly to mask the effect.
3 Use a small amount of the Noise Filter to further dither the edges of the
I do know that you can send 16 bit files to a printer using Cone's
Piezography system and with the use of quad blacks you should be able to
render more than 256 shades, however I am not sure that the Piezography RIP
allows this...it may just convert the 16 bit to 8 bit... I think I will ask
them about that.
In a message dated 11/9/01 2:20:13 PM, Smieglitz@aol.com writes:
The original file was a series of test gradients (0-255 levels) and squares
(n=101 at 1% ink intervals) generated in Photoshop.
I have had some initial success using the 1160 output with Cone inks/driver
on Pictorico OHP for making digital negatives for use in gum bichromate
printing. Jeffrey tested my files' utility for platinum printing. I do not
see the posteriztion effect he speaks of with my unaided eye (either
onscreen, on a lightbox, or in a gum print), but I suspect he is being much
more critical than I and is certainly using a process and paper which would
reveal minor posterization better than multilayer gum image on dimensionally
unstable rough-textured paper. (My eyesight has also deteriorated slightly
in the past couple years which may also have an impact on discriminating the
effect he speaks of.)
The bottom line is that we are comparing apples and oranges. I would say the
process (with a curve applied) is an excellent option for gum printing but I
leave the assessment of it's utility in other processes to expert printers
(e.g., Jeffrey) familiar with the nuances of their cherished media. I have
not tried the 1160 negatives in other processes.
I will add that previous generations of Epson printers (e.g., 600, 1200
series) could not produce results I found acceptable for cyanotypes and van
dyke brown, but were acceptable for some gumprints. The 1160 combo shines by
comparison for gum negatives. But, as others have noted, there are some
issues with ink clogging, fragility of the output, etc. that need to be
resolved before I'd call it a perfect system. For gum printing I find it
"good enough" for what I have in mind. (Of course, some gum printers use
high-contrast Kodalith negatives for effect, intentionally looking for major
posterizations. "Whatever floats your boat"...)
Film is still the benchmark.
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