[argyllcms] Re: Gutenprint and ink limits.

On 8/8/07, "Gerhard Fürnkranz" <> wrote:

> Yes, of course. If the darkes patch which can be printed
> by the printer/driver/rip deviates from neutral, then a
> profile might even choose a somewhat brighter, but more
> neutral color as "black" (depends on the profiler).

Thanks again. It's nice to have my conclusions verified.



I tested after my last e-mail printing a few different dark cmyk
testpatches.  After goggling the topic I created four different, and I
hoped that one of them is as dark as possible.



$ convert -colorspace cmyk -size 300x300 -density 300
"xc:cmyk(100%,100%,100%,0%)" cmyk-100-100-100-0.tif

  $ convert -colorspace cmyk -size 300x300 -density 300
"xc:cmyk(100%,100%,100%,100%)" cmyk-100-100-100-100.tif

 $  convert -colorspace cmyk -size 300x300 -density 300
"xc:cmyk(0%,0%,0%,100%)" cmyk-0-0-0-100.tif

$ convert -colorspace cmyk -size 300x300 -density 300
"xc:cmyk(63%,52%,51%,100%)" richblack.tif



I printed each of them with cinepaint "direct printing cmyk". The file
cmyk-0-0-0-100.tif was not printed at all with cinepaint. The paper
just spooled through the printer. Photprint printed it. I then created
a bigger canvas with an c0,m0,y0,k100 rectangle inside.  This time it
was printed with cinepaint.



My measurement is taken with spotread, with fwa compensation on the paper.

                        

100-100-100-0.tif       Result is  D50 Lab: 12.148500 -3.201308 -0.708121

100-100-100-100.tif     Result is  D50 Lab: 13.460757 -0.906329 -3.565527

0-0-0-100.tif           Result is  D50 Lab: 19.964830 0.008343 7.505049

richblack.tif           Result is  D50 Lab: 11.210768 -4.049849 1.246078



My conclusion is that the gray step mentioned in previous e-mail is
printed correctly, and I have to figure out how to calibrate
gutenprint, or accept a lab value around 11-13.


Regards
Lars Tore Gustavsen

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