[argyllcms] Canon XPS printer drivers: fake CMYK or rogue CMS?

  • From: János, Tóth F. <janos666@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 21 Sep 2013 18:37:19 +0200

I just bought a cheap Canon multifunction printer and noticed that there is
an XPS driver on Canon's site.

It officially promises nothing else but 16 bit/channel over the default 8
bit/channel GDI driver. But I got curious and tried to print a 16-bit CMYK
test chart to see if it is capable of CMYK printing as an undocumented,
side effect kind of hidden feature. I got excited when it actually printed
a less and a more neutral gray scale alongside the CMY gradients.

However, the CMY colors seemed to have very low saturation when I compared
them to the RGB prints. So, I got suspicious that the XPS driver (while
gladly accepts CMYK or even more channels) simply converts everything to
RGB before it send the raster image to the printer.

I tried a lot of combinations in the driver settings but I couldn't get
saturated looking CMY colors out of the printer while printing from CMSK
documents. To make sure, I printed out two small test charts and read them
with my ColorMunki. I created some low quality Lab prifiles with perceptual
gamut mapping for the sRGB color space. The wrl files make it even more
obvious that the CMYK gamut is significantly smaller than the RGB gamut.
(Of course, it isn't physically possible unless there is something going on
in the background.)

The black point luminance was almost the same for both prints (I literally
used the same paper since the small amount of patches fit nicely on an A4

I am still wondering if the printer receives color managed CMYK colors or
RGB colors when I print CMYK colors. I guess it doesn't. However, I don't
know how to prove it since the XPS driver seems to forcefully use an input
color profile.
Even though the test chart is untagged CMYK, the active "working space"
seems to affect the output! So,it looks like the XPS driver always collects
the source color space information, even when I try everything to disable
the CMS in both the printing software and in the printer driver's control

And this also makes me wonder if RGB test charts are also affected by this
undefeatable rogue CMS.

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