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Author Topic: Custom Profiles - one versus the other  (Read 3882 times)
ThePhotoDude
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« on: July 18, 2009, 03:30:29 AM »
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I create a custom profiles on my Z3100 with onboard spectro.

I created two profiles on same paper, settings etc etc:

Number 1: 918 patch provided by HP with their APS
Number 2:  1728 patch from the Bill Atkinson website

I graphed them and the results are confusing ...

[attachment=15500:graph.gif]

The Solid Green is from profile 2, the red wireframe is from profile 1.
You can see that profile 1 has a larger gamut.

I don't get it. Profiling gone wrong with measurement data?

Any ideas? thanks
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Czornyj
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« Reply #1 on: July 18, 2009, 04:46:54 AM »
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Quote from: ThePhotoDude
I create a custom profiles on my Z3100 with onboard spectro.

I created two profiles on same paper, settings etc etc:

Number 1: 918 patch provided by HP with their APS
Number 2:  1728 patch from the Bill Atkinson website

I graphed them and the results are confusing ...

[attachment=15500:graph.gif]

The Solid Green is from profile 2, the red wireframe is from profile 1.
You can see that profile 1 has a larger gamut.

I don't get it. Profiling gone wrong with measurement data?

Any ideas? thanks

I think it may be a matter of patch number and their placement:
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ThePhotoDude
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« Reply #2 on: July 18, 2009, 05:57:33 AM »
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Quote from: Czornyj
I think it may be a matter of patch number and their placement:

Sorry I don't understand what you mean.
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Czornyj
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« Reply #3 on: July 18, 2009, 06:21:32 AM »
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Quote from: ThePhotoDude
Sorry I don't understand what you mean.

I had assigned some exemplary Z3100 profile to 918 and 1728 targets, then I opened the profile (red shape)  and the targets (color dots) in ColorThink. As you can see, the layout of both target patches is different, so maybe it resulted in different shapes of the gamuts.
« Last Edit: July 18, 2009, 06:22:44 AM by Czornyj » Logged

neil snape
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« Reply #4 on: July 18, 2009, 12:32:33 PM »
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Actually if the device has less than stellar linearity it can very well be that a high patch target results in more accurate but less padded sample vs redundancy  ( noise) in profile creation.
When you measure the 918 with APS  and spectro the profile is calculated with the grid points focused on the sample patches around the grid points with a certain weighting for their values. IF the measures fall into the average they are going to map to a certain value. IF you use a higher patch count that shows some differences in linearity they can influence the boundaries to which they are attached.

I do believe the high patch will be more accurate because the sampling will show some deficiencies in the linearity. Yet it may result in what your CT plots show a slightly reduced gamut and our boundary extensions.
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digitaldog
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« Reply #5 on: July 19, 2009, 12:52:39 PM »
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While more patches in theory would indicate a better result, its also where in color space these patches lie.
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Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
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