Re: Epson Phoro printers - 16 bit?
Re: Epson Phoro printers - 16 bit?
- Subject: Re: Epson Phoro printers - 16 bit?
- From: Graeme Gill <email@hidden>
- Date: Thu, 17 Jul 2003 14:49:42 +1000
Robert L Krawitz wrote:
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From: Ray Maxwell <email@hidden>
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Date: Wed, 16 Jul 2003 10:35:33 -0700
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The real question is does a RIP or Controller maintain more than 8
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bits per channel when selecting a screening tile in the RIP.
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Actually, it's the other way around: even an 8-bit RIP needs more than
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8 linear bits of precision for deciding whether to print a dot. If
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you only had 8 bits, you could not print with less than 1/256 ink
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coverage, which is surprisingly dark, particularly at high resolutions
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on most printers.
It depends on the screening technique chosen. For instance, using
a stochastic or ordered fixed cell screen, it's possible to apply the linearisation
curve to the screen thresholds themselves, giving a high output
resolution (ie. 14+ bit precision output levels for a 167x167 screen),
while the input threshold values are 8 bit. Given the typically high
dot gain of current inkjets at their maximum resolutions, this
is an effective technique. Typically a step wedge of 256 input levels
reproduces with good subjective linearity, and almost imperceptible stepping
(given an effective calibration system to define the curve of course!).
Graeme Gill.
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