Bill, Terry: If I understand Terry's aims correctly, he's hoping to reduce the number of total patches to ease the burden of repeated profiling of large numbers of devices, rather than a scenario that Bill might encounter on one of his flexo presses--a configuration where black is missing and only CMY is present, which would best be handled by a CMY profile. In Terry's case (again, if my assumption is correct), there are other possibilities: One might be simply using a smaller CMYK patch set. True, the distribution of colors might not be theoretically ideal, but suprsingly good profiles can be made from just a few hundred patches, more than good enough for unstable digital presses, for instance. (If they are not unstable they will not need frequent reprofiling, which is the presumed need for the abbreviated chart to begin with). There is still another approach offered by prgrams that optimize or reprofile using very small charts., after having made a good initial profile. These would include the EFI Fiery Color Profiler Suite (for Fiery-controlled press), CGS's front end for certain digital presses, also with iterative optimization, and ColorLogic's standalone Reprofiler app, which uses some smart math to reprofile with a small chart. I've tested with 88 patches and the results are very good indeed. (Disclosure: I have business reationships with EFI and ColorLogic.) Mike Strickler MSP Graphic Services
Message: 1 Date: Thu, 01 Oct 2015 13:39:41 -0700 From: William Whitfield <billw@mlode.com> To: ColorSync-users <colorsync-users@lists.apple.com> Subject: Re: CMY profiles with i1Profiler Message-ID: <2BAF418B-1AEE-43E3-9A6A-5B3F76AF45ED@mlode.com> Content-Type: text/plain; charset=windows-1252
Greetings,
A few months ago I created a “No K” profile by doing just what Liane suggested and we are presently using it on our HP Indigo. Except for dark colors is is hard to tell the difference on the printed pieces between using the 4 color and the 3 color profile workflow.
FYI - I did a bit of experimentation yesterday and tried to make a 4 color profile by first deleting the K channel from the reference file - received error while profile was being made. I then tried leaving the K channel in and made all K values zero - once again received error. Took the time to replace any value in the K channel with a 1% and was able to build a profile from the measurement file without error. So as Terry said it appears that iProfiler needs some values in the K channel.
I have, in Photoshop, used both my 4 color and 3 color profile to convert an RGB test target and both seem to produce values very close to the original RGB lab values - with only the darker colors taking a bit of a hit.
-Bill-
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End of Colorsync-users Digest, Vol 12, Issue 127 ************************************************