[argyllcms] Re: Calibrating problems in darks areas

  • From: Frédéric Mantegazza <frederic.mantegazza@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 4 Jan 2008 08:58:06 +0100

On vendredi 04 janvier 2008, Graeme Gill wrote:

> > Commencing device calibration
> > patch 6 of 6
> > Black = XYZ   0.39   0.44   0.56
> > Red   = XYZ  51.60  27.75   2.90
> > Green = XYZ  36.51  76.75  13.52
> > Blue  = XYZ  20.95  10.65 109.08
> > White = XYZ 104.16 109.82 118.94
>
> The black level seems very high for a CRT. I'd
> expect something like 0.05 to 0.1 for the Black Y value.
>
> How black can you get it if you turn the brightness/contrast
> down a long way ?

Ok, I'll try to do that.

>  > How can you set both?
>
> By doing it iteratively in the order the menu presents it. You'll
> certainly get into trouble if your controls are reversed. Normally
> on a CRT the "brightness" control offsets all the signals,
> while the "contrast" control scales all the signals. It's usually
> easy enough to figure out which knob does what by playing with
> it and observing the display.
>
> The documentation recommends that you at least to black level,
> white point, black level and then check, and continue
> until it's satisfactory.
>
> See <http://www.argyllcms.com/doc7/dispcal.html#Adjustment>

Ok, but I won't be able to adjust individual gain/offset channels... BTW, 
what DE max should I reach on pre-calibration in order to have a decent 
calibration?

> I can't see anything obvious with you attached file. What is
> it meant to show ? Are you sure you haven't simply captured
> the original pixel values, rather than the visible effect
> after calibration ?

This is the original file I use to see the problem. I'll post the converted 
file...

-- 
   Frédéric

   http://www.gbiloba.org


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