[Openicc] Printing targets: App or driver ? Profiling RGB or CMYK

[Jan-Peter Homann]

Hi Alastair,
You made a good point. For a smooth step forward, with current available 
tools and settings (Argyll / Gutenprint), you correct, that profiling in 
RGB based on a good Gutenprint RGB->CMYK Setting is easier for crowd 
profiling, which is quite important for the next months.

Question to Robert Krawitz:
There are a lot of testet Gutenprint settings available, which include 
the Gutenprint specific RGB->CMYK conversion.
- Is it possible to create a Gutenprint "CMYK-only" setting by just 
deactivating the RGB->CMYK conversion ?
- Is it possible to to read easily following parameters from the 
deactivated RGB->CMYK conversion:
     - Black generation settings ?
     - Total ink limit ?
For stepping into CMYK profiling, this could lead to following workflow
- read the Gutenprint settings black geneartion and ink-limit for an 
tested setting
- deactivate the Gutenprint RGB-CMYK conversion
- Print the testchart
- generate profile with similar settings for black generation and ink-limit

Question to Graeme Gill:
Some Ink / Media Combinations need heavy total ink limits. Is it 
possible with Argyll to create CMYK-testcharts which are alraedyoptimize 
for an ink limit and black generation ?

Best regards
Jan-Peter


Am 16.05.11 19:56, schrieb Alastair M. Robinson:
> Hi,
>
> On 16/05/11 18:14, Jan-Peter Homann wrote:
>
>> What is the advantage to profile the printer in RGB-mode, if gutenprint
>> allows it to do in CMYK ?
>
> Why enforce a colour space at all?  Encourage the use of one over 
> another by all means, but don't arbitrarily disallow a colourspace 
> unless you have *very* good reason.
>
> It's much easier to create a good RGB profile than it is a good CMYK 
> profile; for an RGB profile there's just the three-dimensional colour 
> space to worry about.  For CMYK you not only have to sample four 
> dimensions, which requires way more patches, but you also have to 
> consider total ink coverage and black generation functions.
>
> A good CMYK profile may give slightly better results than the canned 
> RGB -> CMYK conversion in the driver (in some cases maybe 
> significantly better, but Gutenprint's RGB->CMYK is pretty good), but 
> the extra effort required to get there will make it less likely that 
> we'll be able to crowd-source profiles.
>
> All the best
> -- 
> Alastair M. Robinson
>


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