[argyllcms] Re: Gamma wrong for calibration curves?
- From: "William Wood" <william.wood@xxxxxxx>
- To: "argyllcms" <argyllcms@xxxxxxxxxxxxx>
- Date: Thu, 30 Nov 2006 21:12:22 -0500
> How are you determining that the gamma of the display after
> calibration is 2.0 ?
Haha! Well, first off, the display darkens when the profile is switched in
(using ACDSee), but to confirm that I used dispcal -r, VERY quickly
reloading the calibration curve in (using DisplayProfile) every time
dispcal switched the color patch. (It would be nice if there was a dispcal
flag to measure the display as calibrated!)
Here's the uncalibrated display result:
I:\Util\Argyll\profiles>..\bin\dispcal -v -d1 -yl -r -p .5,.5,2.0
Setting up the instrument
Place instrument on test window.
Hit Esc to give up, any other key to continue:
patch 3 of 3
Black level = 0.29 cd/m^2
White level = 133.65 cd/m^2
Aprox. gamma = 2.19
Contrast ratio = 461:1
White chromaticity coordinates 0.3317, 0.3510
White Correlated Color Temperature = 5535K, DE to locus = 7.3
White Correlated Daylight Temperature = 5536K, DE to locus = 3.2
White Visual Color Temperature = 5352K, DE to locus = 7.0
White Visual Daylight Temperature = 5464K, DE to locus = 3.1
The instrument can be removed from the screen.
Here's the calibrated display result:
I:\Util\Argyll\profiles>..\bin\dispcal -v -d1 -yl -r -p .5,.5,2.0
Setting up the instrument
Place instrument on test window.
Hit Esc to give up, any other key to continue:
patch 3 of 3
Black level = 0.30 cd/m^2
White level = 132.47 cd/m^2
Aprox. gamma = 2.01
Contrast ratio = 442:1
White chromaticity coordinates 0.3328, 0.3508
White Correlated Color Temperature = 5490K, DE to locus = 6.6
White Correlated Daylight Temperature = 5491K, DE to locus = 2.4
White Visual Color Temperature = 5327K, DE to locus = 6.4
White Visual Daylight Temperature = 5439K, DE to locus = 2.3
The instrument can be removed from the screen.
You can see the gamma changed from 2.19 to 2.01 with the calibrated
display.
- Bill
----Original Message----
From: argyllcms-bounce <argyllcms-bounce@xxxxxxxxxxxxx>
Sent: 11/30/06 07:35 PM
To: argyllcms <argyllcms@xxxxxxxxxxxxx>
Subject: [argyllcms] Re: Gamma wrong for calibration curves?
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
william.wood@xxxxxxx wrote:
> On my system, a ThinkPad T42p with Flexview 1600x1200 LCD display, the
> DISPCAL program tends to produce calibration curves at about 2.0 gamma
> instead of 2.2 gamma (the default). Then when the profile is applied to
an
> image the gamma seems to be corrected by the profile back to about 2.25
or
> so. Is this the intended behavior, am I doing something wrong, or is
there
> some other explanation? Thanks,
There is some fun and games with how the black point is handled
(do you subtract the black point from everything, or ignore it
and aim zero at absolute black ?), but no, it's not meant to
be like that.
How are you determining that the gamma of the display after
calibration is 2.0 ?
Graeme Gill.
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