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

  • From: János, Tóth F. <janos666@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 9 Apr 2012 01:12:20 +0200

The profile validation report seems to use java scripts. (Hah, may be
I am wrong about that. I am not a real programmer.)

If you take a look at these "profile validation reports" I am sure you
will figure it out how I tried to use them to calibrate an HDTV (in
this case, a Samsung 51D550 PDP with cheap MStar chipset - the D8000
with Samsung chip is different...).


And here is the test chart and the report style I used (thanks to
Florian for providing these with the absolute targets!):


In short:
- I connected a laptop (HDMI-HDMI cable) and I installed the "Rec709
Gamma 2.4" profile for the display device in the OS.
- I did a pre-cal measurement (actually two in this case because I was
curious if the main board and logic board updates change anything
about the colors).
- I repeatedly ran this profile verification (with a little smaller
test chart, actually) and iterated the displays settings until I
decided it's good enough. (I didn't upload the intermediate steps. It
took about 18 iterations but the last few were worthless. I just
experimented if it gets better or not.)

As you can see, this HDTV have problems with colors.
But I also had problems with deciding about the adjustments.

Problem 1:
Panasonic T IVs offer HSL color controls and I see HSL deviations in
these reports.
But Samsung TVs have RGB color settings which is hard to guess from
HSL deviations (not impossible but requires some brain-work for CMY).

Problem 2:
Some TVs offer 10p gray-scale adjustments.
But it's hard to guess better RGB settings from these reports (HSL
deviations - It's actually looks impossible for me...).

So, I guess it would make this process more user-friendly if someone
could add RGB color bars, % numbers or whatever which show how much R,
G or B should be added to a color to meet with the absolute target
(the Rec709 Gamma 2.x profile).
(Similarly to how dispcal guides you during the interactive white
point adjustment. It shows if you need Red, Green or Blue...)

Otherwise, running this profile evaluation doesn't take more time than
a gray-scale reading in CalMan (unless you have a remote controllable
and very fast pattern generator) but tells you much more.
(Plus it's free and ArgyllCMS uses these relatively cheap calibration
sensors better than CalMan or ChromaPure with X-Rite drivers...)

2012/4/4 Kristian Jörg <krjg@xxxxxxx>:

> For other maybe reading this I speak of a Panasonic VT30.
> For the other question. It so happens that I am a Java + HTML programmer...
> :)
> What exactly did you have in mind. I did not get it from your explanation.
> DispcalGUI is writen in Python btw...

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