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Author Topic: FYI - i1Studio - the ColorMunki Photo update  (Read 23103 times)

Doug Gray

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #60 on: November 06, 2017, 02:41:06 pm »

Then this begs the questions:


1. Without PRMG, what does a V4 profile offer today that a V2 doesn't and who's package provides those option? Specifics on X-rite's product would be ideal if available since that's the overall topic here.
McDowell's update from 2007 states:

>Why was a Version 4 revision of the specification
necessary? It had become apparent that the Version 2 specification gave rise to a number of problems. The main issue was that different color management systems could produce different results, depending on the particular vendor’s interpretation of the specification.

>This was particularly a problem with the perceptual rendering intent, where the specification was not clear on how to handle gamut differences between source and destination.

>There were also different interpretations of how to handle the PCS illuminant and media white point, particularly for display profiles. It was generally agreed that the specification also had a number of minor ambiguities which needed to be resolved.

Quote
2. If the structure (version) isn't an issue in what can build a profile with the PRMG, who does build profiles with it? If no one, does that mean it's not as useful as it's meant to sound?

Well, 10 years later essentially nothing has been done to utilize the PRMG concept with Perceptual Intent. Likely because virtually every application that used ICC profiles explicitly (Photoshop especially) was not willing to make the changes required to link source and destination through the PRMG. Quite possibly because doing so would have radically changed what people were already working around using wider gamut spaces and such. In any case Photoshop's usage of profiles still carries no information as to the source gamut so it would be rather hard for them to change that. Better is sometimes the enemy of the good.

OTOH, at least display profiles are being treated much more consistently and the Colorimetric printer intents have been clearly specified. Of course that was done in the last revisions to V2 profiles. Profiles that adhered to the last V2 specification are said to be V4 compliant.
« Last Edit: November 06, 2017, 04:05:15 pm by Doug Gray »
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GWGill

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #61 on: November 07, 2017, 02:37:38 am »

1. Without PRMG, what does a V4 profile offer today that a V2 doesn't and who's package provides those option? Specifics on X-rite's product would be ideal if available since that's the overall topic here.
Advantages are subtle, and mainly in terms of extra tags that allow a richer description of various transforms. Other changes were mostly gratuitous. ICC MAX is more interesting in the long run, but there's no particular reason to migrate in that direction if you are doing conventional things like print and display profiling.
Quote
2. If the structure (version) isn't an issue in what can build a profile with the PRMG, who does build profiles with it? If no one, does that mean it's not as useful as it's meant to sound?
It's a mixed bag in my view. Having a documented intermediate gamut is better than undocumented proprietary intermediate gamuts or nothing at all if you are randomly mixing and matching (sort of) perceptual transforms, but the fundamental illogic of attempting to do gamut mapping in two independent steps still applies - it can't be done for the general case. To do a nuanced, accurate and flexible gamut mapping requires the gamut mapping algorithm to be able to see both the source and destination gamuts.
« Last Edit: November 07, 2017, 06:24:55 pm by GWGill »
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GWGill

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #62 on: November 07, 2017, 02:41:34 am »

Well, 10 years later essentially nothing has been done to utilize the PRMG concept with Perceptual Intent. Likely because virtually every application that used ICC profiles explicitly (Photoshop especially) was not willing to make the changes required to link source and destination through the PRMG.
I don't think that's the case - using the PRMG doesn't change how the profiles are linked, it just describes a gamut that the A2B transforms to, and the B2A transforms from. So feed Photoshop V4 profiles that use the PRMG and Photoshop will happily use them.
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digitaldog

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #63 on: November 07, 2017, 10:59:04 am »

Thanks for the insight, good to know it's probably not going to happen and that it doesn't really need to  ;D
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digitaldog

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #64 on: November 07, 2017, 10:59:43 am »

I don't think that's the case - using the PRMG doesn't change how the profiles are linked, it just describes a gamut that the A2B transforms to, and the B2A transforms from. So feed Photoshop V4 profiles that use the PRMG and Photoshop will happily use them.
That's my understanding too, but difficult to test since I have no such profiles with a PRMG.
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Doug Gray

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #65 on: November 07, 2017, 11:05:33 am »

I don't think that's the case - using the PRMG doesn't change how the profiles are linked, it just describes a gamut that the A2B transforms to, and the B2A transforms from. So feed Photoshop V4 profiles that use the PRMG and Photoshop will happily use them.
And that's the problem. For instance if you have a wide gamut monitor and image in sRGB how are the colors displayed on the monitor? If you have two monitors, one a wide gamut and one sRGB do expect the image to appear the same on the two monitors? Photoshop users have a long history of expecting the images to appear the same. Or perhaps that's your point.

People are used to display profiles being colorimetric in Photoshop for all intents. They expect a set of RGB values in Adobe RGB that produce the same color as another set in sRGB to continue to produce the same color. What values should show up in Photoshop's info? Colorimetric, or PRMG mapped? What about Lab values?  What happens when you copy layers from a different colorspace? Colorimetric is pretty baked in assumptions about display and working spaces in Photoshop.
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Doug Gray

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #66 on: November 07, 2017, 12:43:02 pm »

Having a documented intermediate gamut is better than undocumented proprietary intermediate gamuts or nothing at all if you are randomly mixing and matching (sort of) perceptual transforms, but the fundamental illogic of attempting to do gamut mapping independently in two independent steps still applies - it can't be done for the general case. To do a nuanced, accurate and flexible gamut mapping requires the gamut mapping algorithm to be able to see both the source and destination gamuts.

That's right and even for V4 profiles tagged for the optional PRMG 6.3.3.1 points out that Perceptual, V4  tagged PRMG is still proprietary and PRMG is a fuzzy target:

Quote
Perceptual rendering remains a proprietary art
....
It is not practical or desirable to specify standard perceptual rendering algorithms. Consequently, it is also not practical or desirable to require that perceptual rendering intents match an exact perceptual intent reference medium gamut (PRMG).

So on top of the fact that the source gamut remains unknown to the destination profile there is no consistent representation. Just fuzzy goals and everyone's proprietary, secret sauce. Lot's of that going on in printer driver selected color management.
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StephaneB

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #67 on: November 07, 2017, 05:08:15 pm »

For a great many intents and purposes went out with the dodo bird. My time would be much better spent learning Mandarin or Cantonese and operating software with user-friendly GUIs.

The thing is, in the case of Argyll, the CLI part does not that all that much time. There are well written tutorials available, from which you can copy the commands verbatim.

By (very) far, most of the time is spent measuring the targets, as I have an old Gretag Macbeth Eye-One. Now that I have a document with my ready-made commands, I think issuing the commands actually takes less time than using a GUI. And certainly much less time than writing about it on a forum  ;)

And the software is really, really good. Totally reliable in its way of working as well as in the quality of the generated profiles. When I print or display test images with very long gradients, they display and print with no defect, no visible non-linearity, which is more than I can say of the profiles I got from the software that X-Rite bundles with the Eye-One.

For printing, using a large numbers of grey patches in the targets gives profiles that work for B&W as well as for colour. It is spectacular.

Getting first class profiles is well worth writing down a few lines or keeping a bookmark to a tutorial in my opinion.
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Mark D Segal

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #68 on: November 07, 2017, 05:12:29 pm »

You may be right Stephane - but one of these days it would be nice to see a well-designed results-oriented shoot-out between Argyll and i1Profiler. Any one game?
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Alan Goldhammer

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #69 on: November 08, 2017, 09:25:59 am »

You may be right Stephane - but one of these days it would be nice to see a well-designed results-oriented shoot-out between Argyll and i1Profiler. Any one game?
While interesting, it would require targets to be printed out from the same printer, measured with the identical spectro and then carried through with both software packages.  I don't own iProfiler and would not be able to do this.  I think that Ethan Hansen has done some comparisons and posted about this.  However, I don't know whether it was a direct "shoot-out"  Perhaps he can weigh in.
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digitaldog

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #70 on: November 08, 2017, 10:48:16 am »

While interesting, it would require targets to be printed out from the same printer, measured with the identical spectro and then carried through with both software packages.
Just share some CGATs data between the two applications, roll some profiles. What settings to use? Now the analysis, that's the real difficult part here considering so much of this is subjective, especially if you intend to test the Perceptual tables!
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GWGill

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #71 on: November 08, 2017, 06:26:53 pm »

Just share some CGATs data between the two applications, roll some profiles.
Charts are part of the equation though. A while back, in a different sphere (TV calibration/profiling) there was the situation where ArgyllCMS had noticeably better accuracy than a commercial product when each was using their own test charts (same number of samples of course), yet when the other product used an Argyll test chart, it's accuracy began to approached that of Argyll :-)
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Doug Gray

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #72 on: November 08, 2017, 07:13:21 pm »

Charts are part of the equation though. A while back, in a different sphere (TV calibration/profiling) there was the situation where ArgyllCMS had noticeably better accuracy than a commercial product when each was using their own test charts (same number of samples of course), yet when the other product used an Argyll test chart, it's accuracy began to approached that of Argyll :-)

I'm in the process of testing this now using charts with 15 equ spaced grid points made in Matlab. This spaces them at 255/14 intervals. Additionally I added grid points along and beside the neutral axis at 255/28 spacings. These were rounded and output to a CGATS file which was used with I1Profiler and Argyll.

I'm testing the profiles with a 9800 using a reference set of LAB colors that are in gamut and at intervals of 10 on the L*, a* and b* axis using Abs. Col. Additionally, a set of neutral patches are added from L*=5 to L*=95 in steps of 2.5 to analyze how well the neutral axis is rendered.  Should be interesting.

Note that this only considers the BtoA1 profile table which is used for both Rel Col and Abs Col. It will also be restricted to in gamut colors so OOG mapping smoothness may or may not differ significantly. I may also look at Perceptual but that is highly subjective. However, on about half the profiles I've made with I1Profiler there are significant mapping anomalies in the Perceptual tables which I've posted images of elsewhere here. No idea if they will show up on any of these though they tended to be more prevalent on profiles made with patch sets that included extra neutrals and near neutrals.

My reference set of LAB colors described above consists of 426 LAB patches and additional neutral patches from L*=5:95 in steps of 2.5.  Matlab creates a tiff file at 720 DPI in 16 bit ProPhoto RGB in i1iSiS readable format. I shall post that together with a CGATS RGB file for those that wish to run their own tests on any profile and have an i1iSiS. It fits nicely on the top half of a 8.5x11 letter page so you can test 2 profiles with just one sheet.
« Last Edit: November 08, 2017, 07:29:39 pm by Doug Gray »
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digitaldog

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #73 on: November 08, 2017, 10:06:33 pm »

Charts are part of the equation though.
So use Argyll chart for both.
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Doug Gray

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #74 on: November 09, 2017, 01:13:05 am »

Preliminary results using Epson 9800 with Costco Glossy and M2 (uV cut) measurements.

I made an I1Profiler profile using defaults except for selecting V2 instead of V4 and max quality for the LUTS. This creates LUTs with 37 grid points. I also made 3 Argyll profiles. The default LUTs, "high" and "ultra." These have 17, 33, and 45 grid points respectively. Note that "ultra" is strongly discouraged. It's also very slow.

Argyll has numerous options for determining Perceptual and Saturation intent tables. The default, where no Perceptual mapping is selected, is to create identical tables to Colorimetric. I have not explored the Perceptual gamut options.

All profiles were correctly generated and didn't map paper black point to L=0. That is they did not incorporate BPC which, for instance, the canned profiles that came with my 9800 did.

All Argyll profiles produced better neutral tone tracking than the I1Profiler profile. However, the I1Profiler produced the lowest overall error for the 426 Lab patches which broadly cover the printer's gamut.

Ave dE00 for the 426 Lab patches
  Argyll -qm: 0.6709
  Argyll -qh: 0.5041
  Argyll -qu: 0.5420
  I1Profiler HighQual: 0.4815

Ave dE00 for the 37 neutral patches from L=5 to 95 in steps of 2.5
  Argyll -qm: 0.6309
  Argyll -qh: 0.4653
  Argyll -qu: 0.4811
  I1Profiler HighQual: 0.6708

Much of these errors, albeit small, are due to the 9800 printer itself. The i1iSiS is an exceptionally consistent instrument that contributes negligibly to the variance but the printer, and to a lesser degree the paper are larger intrinsic sources of error. Both programs have options, the Argyll one better described, to accommodate these errors but I have just used the defaults for this comparison.

It would appear the defaults result in better use of the additional neutral patches for the Argyll program while the I1Profiler's are better matched to the overall grid spacing.

I briefly looked at how OOG colors were mapped to the gamut surface for the two programs. They are radically different. Particularly at lower L* values. However, it isn't clear which would be preferable. There are likely big differences in how things like synthetic Grainger images would print. Significant OOG issues should always be handled by softproofing in any case.

One other oddity is that the L* tracking at low levels of L* (5 to 15) is significantly better (smoother) with the I1Profiler than Argyll. Even so, the Argyll L* tracking over the entire L* range more than made up, yielding significantly better neutral tracking.

Attached are the tif file that is i1iSiS ready and the CGATS file needed to initialize the chart reader. The CGATS file is not a target file, just a filler to initialize the patch locations. For those interested the RGB values are high resolution ProPhoto and are what produces the LAB values in the tiff image. Setup should be US letter Profile using i1iSiS defaults. The tif file should be printed just as any ordinary image using Photoshop manages color using Abs. Col., and selecting the profile/printer combo to test the accuracy of color reproduction.
« Last Edit: November 09, 2017, 01:48:53 am by Doug Gray »
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StephaneB

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #75 on: November 09, 2017, 03:15:32 am »

Wow! Thanks Doug!
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digitaldog

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #76 on: November 09, 2017, 10:08:45 am »

Much of these errors, albeit small, are due to the 9800 printer itself.
And invisible no?
Quote
However, it isn't clear which would be preferable
We're back where we started it seems.
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StephaneB

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #77 on: November 09, 2017, 10:13:05 am »

All Argyll profiles produced better neutral tone tracking than the I1Profiler profile.

This, for me, is important. I do not know enough to assess if that is what allows me to print great B&W with my Argyll profiles.
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Damon Lynch

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #78 on: November 09, 2017, 11:24:06 am »

Thank you for your review Keith. Keep up the great work! You provide a great service to the photographic community with your reviews.
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keithcooper

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Re: FYI - i1Studio - the ColorMunki Photo update
« Reply #79 on: November 09, 2017, 11:38:33 am »

Thank you for your review Keith. Keep up the great work! You provide a great service to the photographic community with your reviews.
Thanks although I expect my lack of charts/graphs/more charts/analysis won't go down well in some quarters, but then it's not written for the gurus ;-) :-)
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