[argyllcms] Re: 0.60 CMYK profile misshaped

Burckhart Seifert wrote:
After analyzing the result I have decided to profile the new measure file again with Argyll CMS 0.53 before delivering the profile. The reasons are: The preview of 0.60 looks very misshaped in ProfileEditor, in VRML it looks very different to the preview of the same file calculated with 0.53 and I have some results out of tolerance in some patches of the MediaWedge. 

The resulting profiles from the data you provided don't look
that different in VRML. They are a little different in behaviour,
but not grossly so.

Here's the results I get putting 10000 random device values through
the two profiles A2B tables, between V53 and V60:

Verify results:
  Total errors (CIEDE2000):     peak = 5.193954, avg = 1.144390
  Worst 10% errors (CIEDE2000): peak = 5.193954, avg = 2.585372
  Best  90% errors (CIEDE2000): peak = 2.057085, avg = 0.984281

The v53 result is a bit suspect in any case, because the smoothing
level was grossly low, and the profile fitting was stopping
prematurely. It did mean that it better accommodated strange
behaviour from a device, at the cost of poorer smoothness.
Given that, the results with V60 do have quite a large self
fit error (peak 10.5, average 1.93 delta E).

Most of the profile fit errors seem to be near cyan == 100%.
Something funny seems to be going on in that channel at least, as
it approaches 100%. Is there a calibration system on the RIP ?
How are the calibration curves targeted ?

The chart is very regularly arranged, which is often not very
efficient (that's why Argyll generate charts are different).

Although it's a bit of a pain with a strip instrument, more patches
may help accuracy, particularly if proofing is the aim. I generally
like about 3000 for a CMYK device.

Graeme Gill.

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