[argyllcms] Re: hplip printer driver and color management

On Monday 08 September 2008 09:01:02 am Milan Knížek wrote:
> Hello Hal,
>
> thanks for answering
>
> Hal V. Engel píše v Út 02. 09. 2008 v 13:15 -0700:
> > There are currently no end user tools for doing linearization with the
> > GutenPrinter drivers.
> >
> > I would expect that most GutenPrint users on this list also use their
> > printers as CMYK devices.
>
> What kind of colour mode do you use for CMYK printing?
>
> The "uncorrected" one is supposedly for users that want to create own
> profiles, while "raw" expects the user to additionaly take care about
> ink limits and linearisation. (According to Gutenprint 5.0 User's Manual
> by Robert Krawitz.)
>
> Since CMYK profile generation requires ink limit as an input parameter,
> I would expect that "uncorrected" mode should be avoided in preference
> of "raw". However, it would require to handle the linearisation outside
> of gutenprint - which is not available now.
>
> So at the end, we are back to "uncorrected" mode and could have issues
> with double use of total ink limits - in profile and gutenprint (where
> it is unclear to me what the default settings for a particular paper/ink
> combination are).
>
> Am I right?

I have been using "uncorrected" but with tweaks to some of the settings such 
as density (I set these higher than the default values for CMY and much higher 
for K) and the ink limits (generally lower than default).  I found the "raw" 
mode to be too difficult to deal with mainly because the linearization curves 
used by gutenprint are very curved (for want of a better term) and in raw mode 
you start out with no ink limits and no linearization and the printer dumps 
huge amounts of ink on the paper.  In other words it is very difficult to set 
up working linearization curves and ink limits in raw mode and I concluded 
that I would be hard pressed to do a better job of setting these than what I 
get with the "uncorrefcted" mode at least with the available tools.  

I am not sure that there are "issues with double use of total ink limits".  As 
part of the profiling work flow you can set a total ink limit for the target 
and profile in targen but you can also override this in colprof.  The 
documentation for targen says that you should set this to be "at least 10% 
higher than the ink limit that will be applied when making the resulting 
profile".  I think this is to avoid generating patches that fall way outside 
of the physical ink limit of the printer/media but that still produce patches 
at the limit.  As an option  you can also have targen use a conditioning 
profile for estimating the ink limits.   

I think the main consideration is that the total ink limit used for creating 
your targets and profiles should be slightly higher than the total ink limit 
setting used in gutenprint.  This will result in profiles that create CMYK 
values that use the full range of the printer gamut right up to it's physical 
ink limit (as set in gutenprint).   In other words the gutenprint ink limts 
are to prevent the printer from using too much ink and the ink limits used in 
targen and colprof are to create profiles that use the full range available 
for the printer.   Graeme is that correct?

>
> (Sorry for getting off-topic.)

I don't think this is off topic since it is about how to create printer 
profiles and how to setup the print drivers as part of that process.

Hal

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