[argyllcms] Re: [argyllcms] Re: RGB Printer profiling and ColorSavvy CM2C
- From: "Gerhard Fuernkranz" <nospam456@xxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 2 Aug 2005 10:52:46 +0200 (MEST)
> --- Ursprüngliche Nachricht ---
> Von: Graeme Gill <graeme@xxxxxxxxxxxxx>
> > *Wow*. My maximum is typically over 5. (forget the average)
>
> That's pretty usual for an inkjet device. It comes down somewhat to
> the repeatability of the print process, as well as the instrument,
> as well as across page uniformity. Some processes (such as
> chemical proofing) have much lower numbers, because it's
> more uniform. Things like xerographic copiers have higher
> numbers, because the process is more variable.
These nubers seems to correspond to mine as well. And I can confirm that I
also got a better fit for the measurements of photochemical prints from the
print lab (I assume they print on Frontier) than for for my inkjet.
Furthermore I've also the impression, that an inkjet, directly driven with
CMYK yields a better fit than with the RGB printer driver, wich is a bit of
evidence, that the RGB profile probably also contains a larger systematic
error in some sectors of the color space, than the CMYK one.
For Evaluation, an interesting test might indeed be to print a set of
patches e.g. N times (e.g. 10 times), with different spatial randomization,
measure the N prints and compute repeatability statistics.
If the profile eventuelly reports a significantly lower avarage error than
the repeatability, then it rather fits the noise in the data and does not
really characterize the device more accurately.
If repeatability statistics are available for the measurements, they could
even be used to guide profile generation (-> e.g. to give a lower weight to
highly variable patches, and to guide the smoothness trade-off). Obviously,
CGATS files do define fields for the standard deviations, but it looks like
Argyll does not make use of them.
Regards,
Gerhard
--
Gerhard Fuernkranz
nospam456@xxxxxx
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