Re: D65 exported data
Re: D65 exported data
- Subject: Re: D65 exported data
- From: "dpascale" <email@hidden>
- Date: Tue, 2 Jun 2009 09:59:40 -0400
Steve,
When exporting Lab values from MeasureTool you are getting "raw" D50 and
D65 flavors of Lab, as expected.
Agreed.
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.
Agreed that it is not correct, but, just a precision:
Assuming all L*a*b* data is D50 is a problem across the industry (of course,
we know that D50 is intended 99% of the time, so it minimizes the problem
most of the time). The problem is compounded by the fact that we can find
many ways of specifying the Illuminant in the file, most of them not
adhering to standards. This is why, when opening a file in PatchTool, the
program asks for the Illuminant if it is not found in the file.
In MeasureTool, the information telling us that the data comes from D65 is
provided by a separate section at the end of the file
BEGIN_DATA_EMISSION
KEYWORD "SampleID"
KEYWORD "SAMPLE_NAME"
NUMBER_OF_FIELDS 38
BEGIN_DATA_FORMAT
SampleID SAMPLE_NAME nm380 nm390 nm400 nm410 nm420 nm430 nm440 nm450 nm460
nm470 nm480 nm490 nm500 nm510 nm520 nm530 nm540 nm550 nm560 nm570 nm580
nm590 nm600 nm610 nm620 nm630 nm640 nm650 nm660 nm670 nm680 nm690 nm700
nm710 nm720 nm730
END_DATA_FORMAT
NUMBER_OF_SETS 1
BEGIN_DATA
1 D65 49.9900 54.6600 82.7700 91.5000 93.4500 86.7000 104.8800 117.0200
117.8200 114.8700 115.9300 108.8200 109.3600 107.8100 104.7900 107.6900
104.4100 104.0500 100.0000 96.3300 95.7900 88.6800 90.0000 89.6000 87.7000
83.2800 83.6900 80.0200 80.2100 82.2700 78.2800 69.7200 71.6000 74.3400
61.6000 69.8800
END_DATA
END_DATA_EMISSION
This data is not read by most programs since it is not standard. It would
have been simpler to specify it in the CGATS Illuminant field, but CGATS
standard is often loosely interpreted and improvided with, so much so that
many simplyfying assumptions must be used when opening the file.
Danny
----- Original Message -----
From: "Steve Upton" <email@hidden>
To: <email@hidden>
Sent: Tuesday, June 02, 2009 1:14 AM
Subject: Re: D65 exported data
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
--
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden