[argyllcms] Re: testing printer profile with a set of XYZ colours
- From: Iliah Borg <ib@xxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 29 Jan 2011 10:44:38 -0500
Dear Klaus,
>> Suppose I need to check a printer profile for reproduction of a set
>> of about 500 pre-determined colours; colours being defined as XYZ D50
>> 2 degree.
>>
>> As a first step, I filter off the colours that are out of gamut
>> using xicclu -fif -ia -pX
>
> This is a pragmatic way to check if the colors are in gamut. I tried out
> others, but came back to it as it is quick and easy.
>
> Please note that you have to use -fb (lower precision) or specify the
> original separation parameters if you want to use them with xicclu -fif.
> Otherwise you use xicclu's defaults (-kr, estimated TIL, no black ink
> limitation). Separation parameters may affect the gamut, especially in dark
> areas.
Yes, of course, separation parameters are to be included for CMYK printers.
>
>> Next, for those XYZ that fall into the gamut I convert them to RGB
>> xicclu -fb -ip -pX
>
> Why perceptual? Do you want to investigate gamut mapping?
I actually run it with all 3 intents to have an idea of mappings. As the list
is already inside the gamut results from comparing runs with different intents
are quite interesting to me. -p resulted in the least deltaE 2000.
>
>> From the RGB list I
>> make a target formatting to CGATS and using ColorPort, print it,
>> measure it, and compare resulting XYZ numbers to source XYZ.
>
> I'm not quite sure what you are after. If it's just the profile you want to
> test, I'd skip the printing and measurement part and just complete ther
> "round trip" with another xicclu call. Otherwise you bring additional
> unknowns into play (printer repeatability, measurement uncertainty)
For this case I'm after the check how the actual printer behaves. Doing several
runs of printing and measuring I see deltaE between runs peaking at 5 with 3
being an average. The task is to evaluate a prototype of a new printing
system. All usual visual checks of this system profiled using Argyll are very
good
> If you really want to test the complete workflow, you can of course also use
> Argyll's tools (printtarg and chartread) to create and measure the target.
The problem with using chartread here is that it does not support neither my
iCColor nor Barbieri.
--
Iliah Borg
ib@xxxxxxxxxxx
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