[argyllcms] Re: How about the following result for Samsung XL20

-------- Original-Nachricht --------
> Datum: Tue, 21 Apr 2009 12:42:19 -0500
> Von: Leonard Evens <len@xxxxxxxxxxxxxxxxxxxxx>
> An: argyllcms@xxxxxxxxxxxxx
> Betreff: [argyllcms] How about the following result for Samsung XL20

> >>From previous attempts, I know I can get the white
> chromaticity closer
> to 0.33, 0.33, with smaller DEs to locus, by adjusting the R, G, B
> settings. Is that worth doing?

Basically I'd say, well why not?
[about 0.5 ... 1 dE seems to be indeed achievable]

On the other hand I'm still not sure, whether the R, G, B gains (in Custom 
mode) adjust only internal LUTs or the backlight.

My feeling was that in some situations, while adjusting the gain, the white 
background of the OSD appeared brighter than the currently set monitor WP, 
which would be certainly an indication that not the backlight, but the LUTs are 
being adjusted. But when I tried to pop-up the OSD again and to verify this 
again, this effect was not reproducible. So I'm a bit confused, either this was 
just a mis-perception of my eyes, or I could also imagine that the adjustment 
is initially done via the LUTs (while the OSD is on), but eventually (when the 
new settings are stored) converted to a backlight adjustment. I'm not sure. 
This certainly needs further investigation...

But anyway, even if RGB gain is still adjusted via the internal LUTs, it's IMO 
better to do it with 14-bit LUTs, than with 8-bit ones in the graphics adapter 
(unless of course you don't care at all whether you hit the locus exactly...)

> One other comment.   The monitor has an `Indicator' setting, which
> accoring to the user's guide doesTurns all LEDs On or Off. If it seems
> that the light from the
> "LEDs affects the brightness of the LCD, you can turn off
> the power to them by setting the Indicator to Off. When
> setting it to On again, all LEDs will again operate in
> accordance with the change in monitor status."
> 
> I'm not sure I understand this, but I did it anyway.  Nothing very
> obvious happened when I went to off and than back to on.

I guess the message means, that particularly in a dark environment, the light 
from the indicator LED may disturb the adaptation of your vision.

> I was having a subtle problem. I was seeing slight variation in tint
> and other artifacts in my desktop background gray.  I wasn't sure if it
> is actually there or the result of some color adaptation in my eyes
> since what I say changed when I closed one eye or the other.  But after
> using the Indicator, uniformity may have improved somewhat.  
> 
> I've noticed similar artifacts on other LCD screens.   Has anyone else
> seen anything like this?

The uniformity is certainly not perfect. It can be compensated with NCE by 
measuring either 9 (3x3) or 15 (5x3) regions on the display surface. I'm not 
sure, wheter only the brightness is compensated, or the tint as well. In the 
I²C traffic it looks like 45 values are transmiteed to the monitor, so I guess 
that there exist either not just 15, but 45 regions which can be individually 
adjusted, or that the gain of all three channels can be adjusted for 15 regions.

Regards,
Gerhard

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