Re: conversion of printable colours
Re: conversion of printable colours
- Subject: Re: conversion of printable colours
- From: Graeme Gill <email@hidden>
- Date: Sat, 17 Apr 2004 11:33:16 +1000
- Organization: Color Technology Solutions
John Swift wrote:
I am really just trying to figure out the science of it. The only tone
this printer cant apparently produce is L*6, so why, when using
relative intent, which as you say does not compress, wont it print L*
8 to L* 18 as the control signals demand. Doesnt the fact that it
produces these tones when using perceptive intent indicate that it can
physically produce them?
Possible reasons:
* Printers use clut tables, and they have discrete data points in them. At the
edges of the gamut, the discrete points mean that a perfectly sharp "cliff" edge
can't be represented.
* The L values may map into quantized device values, and the L values you want, may
not be representable (ie. L*6 maps to K = 253, and :*18 maps to K = 252)
* Poor profile choice of device values leading to a similar situation to above,
ie L*6 maps to CMYK 92 92 92 92. and L*8 to L*18 map to CMYK 91 91 91 91
* The device may be non-monotonic in that area, meaning that the device values
that print L* between 8 and 18 are not between the device values that
print L*8 and L*18
* Faulty test point data being fed into the profile maker.
* A straight out bug in the profile creation.
and there may be more that I can't bring to mind at the moment.
Without examining the profile and the test data used to creat it in detail,
it's impossible to say.
Graeme Gill.
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