[argyllcms] Re: My current display profile: banding
- From: "Pascal de Bruijn" <pmjdebruijn@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 24 Dec 2008 13:52:42 +0100
On Sat, Dec 20, 2008 at 4:23 PM, Leonard Evens
<len@xxxxxxxxxxxxxxxxxxxxx> wrote:
> I still don't understand what is going on with my calibration/profiling
> attempts for my Samsung 226CW monitor, but I decided to work with it
> for the moment. It still shows what I consider a slight red-magenta tint
> with a grayscale image, but when I try it on the test image produced
> with timage, showing two color cubes with a gray scale between them, the
> gray scale looks fine. So my problem may be some perceptual problem
> with my vision.
>
> But I now have another problem. With the calibration loaded into the
> Video LUT, when I invoke the profile (in this case using inkscape),
> I get some obvious banding which is either absent or minimal when
> the profile is not invoked. I created the profile using targen, etc.
> using -f500 for targen and -qm for colprof.
>
> Any suggestions?
Maybe I'm getting this wrong... But I'm not doing anything with the VideoLUT...
I reset my screen to it's default settings. Then I set the screen
color temperature
to custom settings and equalize the R/G/B channel, usually set them
all to 100 or
255.
Then start dispcal:
# dispcal -v -q h -y l hp
Select option 3, and adjust your screen to a comfortable level of
brightness, in my
case ~300cd/m2, which is currently 68% brightness. Your backlight will dimm over
time, but then you can adjust your brightness back to 300cd/m2 again...
I generally leave the blackpoint just be...
Then run:
# targen -v -d3 hp
# dispread -v -y l -k hp.cal hp
# colprof -v -A "HP" -M "LP2475w" -D "HP LP2475w (`date '+%-e %b
%Y'`)" -C "Public Domain" -r 1 -q u -a s -n c acer
And load the resulting profile into GIMP/Inkscape/Scribus/UFRaw, or whatever...
I don't use xcalib or whatever... Just let LCMS do it's job.
Also please be aware of the fact, that the larger a screen gets to more chance
of banding you'll have... This is just an 8bit limitation, and not
really specific to
color management in general, but color management can worsen the issue.
For example a SVG background with some large gradients on my
1920x1200 screen produces banding even without color management...
Regards,
Pascal de Bruijn
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