[argyllcms] Re: Color errors on < 100% stimulus

  • From: János, Tóth F. <janos666@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 26 Mar 2012 00:56:11 +0200

I still don't understand the so-called „color decoding issue”.
My Pana G30E has relatively good and significantly better color
accuracy than my Samsung D550 had.

2012 won't be very different except the VT50.

75% saturated pattern?
I never heard about such thing. On the other hand, 75% stimulus is
very common for HDTV calibration.

2012/3/21, Kristian Jörg <krjg@xxxxxxx>:
> Graeme Gill skrev 2012-02-13 14:41:
>> Kristian Jörg wrote:
>>> Well, the reason I was a bit unimpressed is because this is supposed to
>>> be one of the very best TV
>>> sets to buy, and it includes full ISF controls for managing grayscale at
>>> 10% stimulus steps. Color
>>> however is only at 100% stimulus. So I can nail in the grayscale and
>>> gamma to mostly perfect result
>>> (according to the patterns used, i.e full windows cause lightness to drop
>>> a bit). Color however
>>> seems a bit more difficult. Now it is possible I have used the CP
>>> software wrongly at the 75% color
>>> intensity. It has a 75% Rec. 709 setting that I assumed should be used
>>> for the 75% W+ 75% RGB
>>> measurements. But maybe I should measure all those at 100% Rec. 709
>>> setting since i assume the Rec
>>> 709 standard is linear? When using 75% patterns all that happens is that
>>> luminocity falls a bit,
>>> but it is all realite to white which is measured as a baseline... ?
>> I'm afraid I have to smile a bit at all that. Rec 709 is an idealised
>> additive display.
>> Idealised displays have a perfect black, something no real display can
>> achieve.
>> So (as usual) you are faced with the issue of how do you deal with the
>> non-perfect black,
>> given that the transfer curve assumes that is is perfect. Non-LCD based
>> displays are not
>> so bad in this regard though. Then there are the viewing condition
>> assumptions inherent
>> in Rec 709.
>> The channel combination targets aren't too hard to compute - add the XYZ
>> of the individual channel
>> target or measurement values, since Rec 709 is additive.
>> Graeme Gill.
> Just a short follow up to this little thread that I started. It was all
> due to a misunderstanding of what patterns to use for the 75% Rec 709
> calibration settings in Chromapure. It should be 75% saturated, not 75%
> intensity. With correct patterns my results where correct. However if
> anybody tries this, there is a confirmed bug with it with at least
> version 2.0.10 (and probably 2.0.11) in CP, so wait for the next release
> before trying this.
> And there is also strong indication of color decoding issues in the 2011
> models of Panasonic plasmas. Something that should be fixed in the 2012
> models. Bummer. There will not be a fix to the 2011 models, or even any
> more firmaware updates at al,l according to those who "know".
> /Kristian

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