Re: D65 exported data
Re: D65 exported data
- Subject: Re: D65 exported data
- From: Michael Eddington <email@hidden>
- Date: Tue, 2 Jun 2009 11:33:25 -0400
Thanks for all the information.
Let me ask this question, what differences would one expect between
D65 lab values derived from spectral data versus D65 values
chromatically adapted from XYZ? For example, say someone is measuring
sample with a handheld with D65 as the user defined illuminant,
versus, spectral data exported out of MeasureTool , PatchTool or
ColorThink. If someone were to set up a workflow for proofing and
process control utilizing D65, what kind of issues could they
potentially run into?
So MeasureTool is deriving D65 from XYZ data rather than from
spectral? Why then is this only an option when spectral data is present?
Mike
On Jun 1, 2009, at 8:23 PM, dpascale wrote:
Hello Mike,
If you compare Lab D50 vs Lab D65 (not spectral data), then the
first set of
differences makes sense, assuming that a proper Bradford transform
was made
betwen the two data sets, so that they are compared under the same
Illuminant (either D50 OR D65).
This is the Illuminant metamerism. (or Color Inconstancy, to be more
specific), since the Bradford transform simulates a perfect match
between
Illuminants, which is different from the actual perceived value
computed
with the spectral data (i.e. your initially exported data which
combines the
Illuminant spectra and the target spectra).
However, I do not understand what exactly you are comparing in the
second
case.
.
Please send me the file and the steps you do in the second part.
Thanks,
Danny
www.babelcolor.com
----- Original Message -----
From: "Mike Eddington" <email@hidden>
To: <email@hidden>
Sent: Monday, June 01, 2009 5:42 PM
Subject: D65 exported data
>I was comparing Lab measurements exported out of Profilemaker
MeasureTool
>ast both D50 and D65, then attempted to do the same within a
ColorThink
>worksheet from a single spectral data set, but got vastly different
>results. I would expect to get the same results.
>
> In the first instance I open a spectral measurement file in
MeasureTool
> and exported both D50 and D65 Lab values, then dropped in a
Colorthink
> worksheet and compared them
>
>
> Next, I dropped the spectral file in a worksheet, then dropped the
same
> measurement file again, and changed the Color setup to CIEstdD65
(6430K)
> and compared. I was expecting near the same delta values as in the
first
> method.
>
> There appears to be a major difference between D65 out of
MeasureTool and
> CIED65 (6430) in Colorthink..babelcolor patchtool have slightly
different
> result to mesuretool.
>
> .anyone care to comment?
>
> Results below:
>
> Exported from MeasureTool and compared in ColorThink:
> --------------------------------------------------
>
> dE Report
>
> Number of Samples: 1617
>
> Delta-E Formula dE76
>
> Overall - (1617 colors)
> --------------------------------------------------
> Average dE: 1.49
> Max dE: 3.70
> Min dE: 0.00
> StdDev dE: 0.82
>
> Best 90% - (1454 colors)
> --------------------------------------------------
> Average dE: 1.32
> Max dE: 2.61
> Min dE: 0.00
> StdDev dE: 0.69
>
> Worst 10% - (163 colors)
> --------------------------------------------------
> Average dE: 2.95
> Max dE: 3.70
> Min dE: 2.61
> StdDev dE: 0.27
>
> --------------------------------------------------
>
>
>
> Calculated D50 and CIEstdD65 within Colorthink and compared
> --------------------------------------------------
> --------------------------------------------------
>
> dE Report
>
> Number of Samples: 1617
>
> Delta-E Formula dE76
>
> Overall - (1617 colors)
> --------------------------------------------------
> Average dE: 10.07
> Max dE: 16.69
> Min dE: 4.20
> StdDev dE: 2.84
>
> Best 90% - (1454 colors)
> --------------------------------------------------
> Average dE: 9.50
> Max dE: 13.92
> Min dE: 4.20
> StdDev dE: 2.39
>
> Worst 10% - (163 colors)
> --------------------------------------------------
> Average dE: 15.10
> Max dE: 16.69
> Min dE: 13.96
> StdDev dE: 0.81
>
>
>
> Mike
>
--------------------------------------------------------------------------------
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