[argyllcms] Re: 1st post
- From: Knut Inge <knutinh@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 8 Dec 2010 10:18:37 +0100
Thank you. I am sorry about this long post, but I tend to think clearer when
I have to formulate my misconceptions :-)
Colorimeters are simulating the spectral response of a standardized human
viewer "long", "medium" and "short" sensory elements, right? While
spectrophotometers are sampling the spectrum at higher resolution then
combining the response into something similar. After som googling, I have
the impression that the Spyder 3 line share the same basic sensor and that
it does fairly well for wide-gamut displays?
How much of this is software? I.e., if I had access to 3 or 4 different
calibration softwares, using my Spyder 3 express, would they give very
different results? I assume that any application with correction matrixes
for my sensor (possibly in combination with WGC displays, or even my model
display) will have an upper hand, but other than that, the profiling is more
mathematics and sensible regularization than magic?
My display came with a color calibration factory report, stating that
Average Delta E was "<5.0" for both sRGB and aRGB profiles (plots suggest
maximum "DeltaE*CIE94" of less than 3, average of 1 or so) using a Minolta
Color Analyzer CA210. It also shows gray-scale tracking and gamma curves,
but I find them hard to make something out of. Evidently, color temperature
is a constant 6500K for grey levels >25, but strays off into cooler values
for grey levels <25.
When my display offers a simulated "sRGB" mode (that from tests is judged as
fairly good), am I right that it is the only way for me to get sRGB
appearance from non-color-managed applications/OS-es? Since ArgyllCMS make
nice profiles that will not be used in that case, and the display
calibration only touches white-point and brightness (no front-panel 3x3
matrix input)? Further, as the display is native 8+2 bits, 12 bits
processing, while DVI is practically limited to 8 bits (displayport does 10
bits, possibly also with this screen but is not recommended by Dell due to
wake up from suspend quirks,
http://en.community.dell.com/support-forums/peripherals/f/3529/t/19339056.aspx),
this might avoid banding issues.
How does ArgyllCMS relate to Madshis MadVR and "3DLUT"? I take it that its
massive 96MB LUT does an exhaustive lookup of every possible "rgb" input to
its corresponding "rgb" output, meaning that no parametric simplifications
have to be made (of course, regularization may come in handy anyways). But
is that approach more suited for movies and other material that adhere to
some agreed-upon standard, while editing photos in Lightroom/Photoshop is
more suited for the real-time color management inside those applications?
What does Wide Gamut really, physically mean? Does it mean that the spectra
of the nominally "red", "green", "blue" primaries are sharper/narrower,
giving less overlap and thereby allowing more saturated colors? When this is
accomplished by swapping back-lighting, does it mean that the backlighting
consists of 3 narrow peaks (meaning that there is little excitation in the
regions where the panel "valves" might overlap)?
Below I have updated the table of measured values with the tftcentral test.
Sadly, both review sites use the Blue Eye pro. Comparing tendencies between
them and me, I find that :
1. They measure my display to be too warm (5700K), while I measure it to be
too cold (6900K)
2. They measure a lower black level than I do, leading to higher contrast
and perhaps gamma issues (?).
http://www.flatpanelshd.com/review.php?subaction=showfull&id=1265617565
http://www.tftcentral.co.uk/reviews/content/dell_u2711.htm#calibration
out-of-the-box measurements:
flatpanelshd TFT Central My calibration
Instrument Blue Eye Pro Blue Eye Pro Spyder 3 express
Black level = 0.23 0.25 0.38 [cd/m^2]
White level = 225 208 242.78 [cd/m^2]
Aprox. gamma = 2.1 1.9 1.80
Contrast ratio = 978:1 832:1 642:1
White chromaticity coordinates
###### ###### 0.2815
###### ###### 0.3378
White Correlated Color Temperature (DE 2K to locus)
8186K (20.2)
White Correlated Daylight Temperature (DE 2K to locus)
8157K (18.9)
White Visual Color Temperature (DE 2K to locus)
6787K (19.8)
White Visual Daylight Temperature (DE 2K to locus)
6904K (18.4)
Color temperature
5867 5504
Display calibration:
Brightness: 22 30 22
Contrast: 50 50 50
RGB: Manually
• R: 88 83 100
• G: 84 94 81
• B: 89 87 83
Calibrated/profiled results:
Black level = 0.12 0.18 0.25 [cd/m^2]
White level = 106 121 116.59 [cd/m^2]
Aprox. gamma = 2.2 (?) 2.2 2.18
Contrast ratio = 883:1 672:1 472:1
White chromaticity coordinates
###### ###### 0.3123
###### ###### 0.3290
White Correlated Color Temperature (DE 2K to locus)
6524K (4.9)
White Correlated Daylight Temperature (DE 2K to locus)
6524K (0.3)
White Visual Color Temperature (DE 2K to locus)
6348K (4.7)
White Visual Daylight Temperature (DE 2K to locus)
6513K (0.3)
Color temperature
6520 6485
-k
On Wed, Dec 8, 2010 at 12:06 AM, Pictus <pictus171@xxxxxxxxx> wrote:
> Hello Knut,
>
> Also check the TFT Central resutls
> http://www.tftcentral.co.uk/reviews/content/dell_u2711.htm#calibration
>
> The Spyder 3 may have problems with Wide Gamut LCD...
> One time I calibrate(Spyder3) a DELL 2709W with ColorEyes Display Pro(they
> have a 10 days trial)
> and the results were good, sadly at that time I did not know
> Argyll/DispCalGui.
>
> Also Quato iColor Display 3 have the correction matrices for wide gamut
> LCD, but I do not know the details...
>
>
> --
> Best regards,
> Pictus mailto:pictus171@xxxxxxxxx
>
>
>
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