Re: Hi-Fi inksets
Re: Hi-Fi inksets
- Subject: Re: Hi-Fi inksets
- From: Graeme Gill <email@hidden>
- Date: Mon, 09 Feb 2004 15:35:32 +1100
- Organization: Color Technology Systems
Robert L Krawitz wrote:
One other thing that I've had good experiences with (mostly for a
different reason) is to use a very good screen (Raph Levien's EvenTone
Screening) with some perturbation. In this case, the purpose of the
perturbation is to break up screening artifacts that create
patterning, but this slight decorrelation may also favorably affect
banding. The EvenTone Screen algorithm suffers from banding more than
the Ordered (farthest neighbor matrix) dither algorithm that's our
mainstay, and watching the printer actually print suggests that this
would be the case. It's very common for something printed with
EvenTone to print the vast majority of its drops in one pass, even if
4 or 8 passes are being used. Ordered dithering doesn't suffer from
this, and is faster. The problem with ordered dithering, of course,
is the noise that's visible in the midtones.
There is a continuum between farthest neighbor and a fixed screen equivalent
of an error diffusion look stochastic pattern. Rather than choose the next level
as the farthest from any other (resulting in ordered dither), choose
randomly from the farthest N, where N tunes the degree of randomness.
There are some additional ways of finessing this, but I'm not going to
tell you what they are :-)
Graeme Gill.
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