Re: Hi-Fi Inksets
Re: Hi-Fi Inksets
- Subject: Re: Hi-Fi Inksets
- From: Robin Myers <email@hidden>
- Date: Thu, 05 Feb 2004 21:14:12 -0800
- Organization: Robin Myers Imaging
Graeme Gill wrote:
Robert L Krawitz wrote:
Cross-plane screening helps most at very low densities (highlights).
The placement error is constant (it doesn't depend upon the density).
So if the placement deviation is on the order of .001", but the
separation between dots is 1/64" (which at 1440x720 DPI corresponds to
a density of about .4%, which is certainly quite visible), the
placement error is negligible compared to the average dot separation.
Good point. So to use this type of screening in the real world, it
would be desirable to
have the different color planes screens de-correlated once the dot
density grow high enough,
thereby getting the benefits in the highlights where it counts,
without triggering banding and pattern
issues.
About 10 years ago a paper was presented by John Dalton of Apple
Computer detailing a method for ordered stochastic screening that
eliminates almost all the problems both Mr. Gill and Mr. Krawitz are
describing. I believe it was presented at either an IS&T, SPIE, or
printing conference. For some unknown reason it has gone unnoticed.
In brief, the algorithm is a method for creating ordered stochastic
screens that show no edge tiling artifacts (the pattern is manipulated
in Fourier space to produce an equal intensity frequency spectrum) and
their use would also solve most of the problems causing color
contamination of neutrals using current stochastic algorithms (such as
debated here about Epson printers).
It is unfortunate that printer or RIP manufacturers have not come across
this paper.
I am not affiliated in any way with Mr. Dalton other than I had the good
fortune to have him show me examples of his invention. Oh, by the way,
the information is in the public domain...hint hint...
Robin Myers
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