Thanks for that Andy, and for all those who responded both on and off
list.
I'm surpised at how non-intuitive this is between applications and
spectros. I would have expected that spectral data exported as D65/2 Lab
values would match measurements offline with a handheld with D65/2
degree settings, but this isn't the case. Spot measurements with an i1
at D65/2 degree between MeasureTool and BabelColor CT&A do not correlate
very well. My 939 correlates well with i1 measurements through
BabelColor at D65/2 degree, so I'm assuming that this is the "correct"
method for measurement. But herein lies the problem of handheld D65
measurements for process control and D65 measurements (from Measuretool)
for color management...apparently apples and oranges.
How would one expect to get chart measurement that correlates with a
handheld spectro considering the different calculation methods?
Mike
________________________________
From: Andreas Kraushaar [mailto:email@hidden]
Sent: Tuesday, June 02, 2009 12:31 PM
To: Mike Eddington
Subject: Re: D65 exported data
On Jun 2, 2009, at 5:33 PM, Michael Eddington wrote:
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?
This is a fundamental difference.
A) gives you the color of your surface (material) under the new
(D65) illuminant
B) gives you the tristimulus values for e.g. D65 that recreate
the same appearance under D50 as you would have seen under D65.
sincerely
Andy
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
>
------------------------------------------------------------------------
--------
_______________________________________________
Do not post admin requests to the list. They will be
ignored.
Colorsync-users mailing list
(email@hidden)
Help/Unsubscribe/Update your Subscription:
@gmx.de
This email sent to email@hidden
Colour of the future - future of colour
http://forschung.fogra.org/index.php?menuid=158
Andreas Kraushaar
Dept. Prepress
Fogra Graphic Technology Research Association
Streitfeldstrasse 19
81673 Munich, Germany
Telefon: +49 89. 431 82 - 335
Telefax: +49 89. 431 82 - 100
E-mail: email@hidden
Internet: www.fogra.org
-----------------------------------------------------------------
This e-mail message may contain confidential and/or privileged
information.
If you are not an addressee or otherwise authorized to receive
this message,
you should not use, copy, disclose or take any action based on
this e-mail
or any information contained in the message. If you have
received this
material in error, please advise the sender immediately by reply
e-mail and
delete this message.
Managing Director: Dr. Eduard Neufeld | Registered Office:
Munich | Register
of Associations: VR 4909