Re: D65 exported data
Re: D65 exported data
- Subject: Re: D65 exported data
- From: Andreas Kraushaar <email@hidden>
- Date: Tue, 2 Jun 2009 07:32:40 +0200
Hi all,
colour (gamut) comparisons make only sense under one state of
adaptation (such as D50 in the PCS colorimetry). If D65 data comes in
(for whatever purpose) it mast be chromatically adapted to D50 (by
one or the other method).
sincerely
Andy
On Jun 2, 2009, at 7:14 AM, Steve Upton wrote:
At 9:42 PM -0400 6/1/09, Mike Eddington wrote:
My intention was to compare only values derived from spectral
data. The second case I was attempting to do this using
ColorThink. Rereading my post, it isn't that clear. Basically I
dropped the same spectral data twice into a single worksheet
(where I would get no delta if I compared), and changed the color
set up on the second color list to CIED65, the enabled delta to
compare.
I'm away from my files, so I can't send them to you now, but will
when I can. If you have any spectral data and color think, you
should be able to see what I'm talking about though.
Hi Mike,
I think I can speak to some of the differences you are seeing.
When exporting Lab values from MeasureTool you are getting "raw"
D50 and D65 flavors of Lab, as expected.
When they are imported into ColorThink (or any other compare tool,
probably) they are treated as if they are the same flavor of Lab
and delta-E is calculated. As far as I know, this is not correct.
ColorThink calculates D50 and D65 as requested and then the D65
values are adapted back to D50 for the dE differencing
calculations. As a result you will also see the "D65" values in
ColorThink are different than what you might see in another tool.
They are post-adapted values. In this manner the dE calcs reflect
the correct comparison (D50 -> D50) and the numbers "make sense" on
screen.
To be honest, this is off the top of my head. I believe that this
is the way it was designed and implemented. I haven't tested it
recently to confirm that it's working as expected.
I hope this sheds some light on the behaviors
regards,
Steve
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