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Author Topic: How to get the minimum L* value from an ICC profile ?  (Read 2196 times)

Doug Gray

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #20 on: April 23, 2022, 09:28:59 pm »

Accurate L* from an ICC profile; what the profile reports and what the profile and printer produce (which itself must be measured) can differ by quite a deltaE.

Ain't that the truth. My 9800 OEM Epson profiles show a L* min of 0.0 for Epson Prem. Glossy. My actual custom profiles show L* min of 3.8 which is also what it actually measures. Using Mark's Photoshop 2 step process.

This is because Epson baked in BPC in their B2A1/A2B1 tables when it is only legit in the Perceptual and Saturation. Not Relative.

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digitaldog

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #21 on: April 23, 2022, 09:35:07 pm »

Ain't that the truth. My 9800 OEM Epson profiles show a L* min of 0.0 for Epson Prem. Glossy. My actual custom profiles show L* min of 3.8 which is also what it actually measures.
More fun, send all the profile target patches used to build the profile through the same measurement analysis. Ouch.   
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Doug Gray

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #22 on: April 23, 2022, 09:45:38 pm »

More fun, send all the profile target patches used to build the profile through the same measurement analysis. Ouch.

I've done that. Reasonably close agreement. Of course I don't have the measurements the Epson profiles were made with. Would be nice but not embedded in their profiles. More disparity with an independent set of patches. How close they match depends on the number of patches the profile was made with. Generally, after more than 1000, improvements are quite small.


See this windows app for creating profiles and comparing profile patch sets. Readme has an extensive description of the program.

https://github.com/doug3236/i1Patches

Program to create patch charts and evaluate profile accuracy
In a single printing pass, create and verify accuracy of one or more ICC profiles from one or more sets of RGB profiling patches.

i1Patches Is a Windows based tool principally used to aggregate and randomize one or more, printer profiling patch sets along with randomly generated patches for independent accuracy verification. It produces tif and CGATs files compatible with XRite's i1Profiler and i1iSis or i1Pro2 spectrophotometers.
« Last Edit: April 23, 2022, 09:57:58 pm by Doug Gray »
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digitaldog

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #23 on: April 23, 2022, 09:53:47 pm »

Of course I don't have the measurements the Epson profiles were made with. Would be nice but not embedded in their profiles.
In some, it actually is! CxF data. From there, using i1Profiler, one can export Spectral Data etc (SC-P800 Series Ex Canvas Natural Satin PK v2.icc) as an example:
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Doug Gray

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #24 on: April 23, 2022, 09:59:34 pm »

In some, it actually is! CxF data. From there, using i1Profiler, one can export Spectral Data etc (SC-P800 Series Ex Canvas Natural Satin PK v2.icc) as an example:

Nice. Too bad my 9800 OEM profiles don't have them. Would be cool to look at.  That said, I don't trust anything I don't make.
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digitaldog

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #25 on: April 23, 2022, 10:18:21 pm »

Nice. Too bad my 9800 OEM profiles don't have them.
IF they have a .v2 in the name, or an X-rite copyright tag, they do.
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Doug Gray

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #26 on: April 23, 2022, 10:22:59 pm »

IF they have a .v2 in the name, or an X-rite copyright tag, they do.

The 9800 profiles were made in 2004 and are version ICC 2.4. IIRC, they were Seiko profiles. Good to see more recent stuff has this. I've also noticed more printer profiles are M2 based.
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digitaldog

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #27 on: April 23, 2022, 10:25:10 pm »

The Seiko profiles kind of suck.  :'(
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Doug Gray

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #28 on: April 23, 2022, 10:31:27 pm »

The Seiko profiles kind of suck.  :'(

Other than they are made incorrectly, I can't really say. Baking in BPC makes it impossible to check accuracy. At least using Abs Col patches. Don't know if why they do that or if it's some sort of option in the profiling s/w. But it's been about 15 years since I've used the OEM profiles.
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MfAlab

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #29 on: April 24, 2022, 03:48:51 am »

Yes, some ICC profiles show results we did not expect. BPC in ICC, M2/M3 measurements...

I check a "normal" ICC generated by caldera RIP (M0 measurement), it uses x-rite's color management core. Under CIED tag, there are all measurement spectrums. I calculated black target readings and averaged, get L* = 4.240. Other methods list below:

PS 2-step convert: 5
PS convert and curve-tool finding 8 bit value: 4.706 (12/255)
ICC bkpt tag: 4.146
ICC A2B1 tag: 4.249
ICC viewer (iccview website or ProfileMaker's Gamut View) can only provide a guess around 4~5.

Using a regulars ICC profile, the A2B1 tag has closest value.
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Gerd_Peters

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #30 on: April 25, 2022, 03:28:03 am »

I've done that. Reasonably close agreement. Of course I don't have the measurements the Epson profiles were made with. Would be nice but not embedded in their profiles. More disparity with an independent set of patches. How close they match depends on the number of patches the profile was made with. Generally, after more than 1000, improvements are quite small.


See this windows app for creating profiles and comparing profile patch sets. Readme has an extensive description of the program.

https://github.com/doug3236/i1Patches

Program to create patch charts and evaluate profile accuracy
In a single printing pass, create and verify accuracy of one or more ICC profiles from one or more sets of RGB profiling patches.

i1Patches Is a Windows based tool principally used to aggregate and randomize one or more, printer profiling patch sets along with randomly generated patches for independent accuracy verification. It produces tif and CGATs files compatible with XRite's i1Profiler and i1iSis or i1Pro2 spectrophotometers.

Hi Doug,

are there binaries somewhere? I could only find project and header files.

Greetings Gerd
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Doug Gray

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #31 on: April 25, 2022, 09:50:32 am »

Hi Doug,

are there binaries somewhere? I could only find project and header files.

Greetings Gerd

Yes, the binary (executable file) is in the "Release" section. Here's a direct link.

https://github.com/doug3236/i1Patches/releases/tag/V1.0.1
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Gerd_Peters

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Re: How to get the minimum L* value from an ICC profile ?
« Reply #32 on: April 26, 2022, 02:34:38 am »

Thanks for your effort...

Greeting Gerd
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