[argyllcms] Re: The different color temperatures: questions

>
> -------- Original-Nachricht --------
>> Datum: Wed, 15 Apr 2009 10:55:21 -0700
>> Von: "Hal V. Engel" <hvengel@xxxxxxxxxxx>
>> An: argyllcms@xxxxxxxxxxxxx
>> Betreff: [argyllcms] Re: The different color temperatures: questions
>
>> I have a Sunsung 245BW and I have played with the controls
>> on it extensively while measuring what the controls actually
>> do.  The RGB controls on this monitor have almost no affect
>> on the white point of the monitor unless I set them to totally
>> crazy settings and even then they only have a slight affect on
>> the white point. I have also done some of the same testing on
>> a few other Sansung LCD monitors with similar results. The RGB
>> controls are much closer to gamma controls for each individual
>> channel and primarily affect the gray and black color balance.
>
> I have briefly investigated my XL20 in Custom mode too. My impression is
> that Contrast and the RGB Color Controls basically do adjust the gain of
> the three channels, however they only work as expected as long as I set
> them to values BELOW the factory default.
>
> When I set them to larger values, then they seem to multiply the signal
> with a factor of > 1.0, but then clip at 1.0, which indeed results in a
> behavior as you described above, i.e. the WP does not change, but the
> mid-tones do.
>
> [I think I had observed a similar behavior on other displays too, but I
> never did care explicitly.]
>
> For my XL20 in Custom mode, the following manual adjustment procedure
> seems to work fine:
>
> 1. reset the color settings to factory defaults
>
> 2. select the color temperature preset closest to the target WP
> chromaticity (i.e. one of warm5, warm5,... cool6)
>
> 3. adjust the RGB gains to fine-tune the WP chromaticity, but only turn
> them DOWN, not up (i.e. one of the R,G,B gain controls can remain at the
> factory default (50 in my case), and the other two ones end up with
> smaller values)
>
> 4. adjust Brightness control to meet the luminance target
>
> 5. adjust Gamma control to meet the gamma target approximately
>
> Iterate steps 3..5 if necessary (since for instance changing backlight
> brightness will slightly change the chromaties too)
>
> [I don't see any need to fiddle with the Contrast, except possibly for
> dark luminance targets, blow the minimum brightness.]
>
> Regards,
> Gerhard
>
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>

Which value of Contrast do you leave it at.   My XL20 came with Contrast
set at 70.

I'm not sure how you set the gamma, say using dispcal.  I did manage to
profile my XL20 with an i1pro using (approximately)

dipscal -o -t 6500 -b 120-g 2.2

In using the script, I followed the steps 1,3,... except for one that
wasn't relevant.   I also found that I had to reduce the RGB values but I
didn't fiddle with warm1,... as you did.

I don't see where in the process you set the OSD gamma value

Did you follow the script just to calibrate, or did you fiddle with the
controls and use dispcal -r to check your progress?

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