[argyllcms] Re: Color errors on < 100% stimulus
- From: János, Tóth F. <janos666@xxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 11 Feb 2012 15:31:18 +0100
No, gamma is far from perfect.
Try to measure the grayscale with very small, normal and full screen
patches. You will get three different gamma curves and only standard
windows size will give you an approximately good enough pure-power
gamma function.
The same goes for the separate red, green, blue gradients. They all
depend on the pattern size and they never really follow the same tonal
response (only "close enough").
2012/2/10 Kristian Jörg <krjg@xxxxxxx>:
> Thanks for the answers regarding profiling. I will not profile the plasma as
> a PC monitor.
>
> About the VT30 I tend to agree. I just learned that there is a special
> firmware that improves color luminance on higher panel brightness. This
> patch is "only" for professional calibrators, and only for the US region.
> Although it is freely downloadable. I could not find a EU version of it... I
> also learned that there will not be further patching done as the VT50 model
> is imminent. :( :(
>
> However I do feel that the controls are effective in what they should do.
> The problem is that the CMS controls one point. The rest of the intensity
> levels are not following suite...
>
> I ended up with a calibration that is no better than the builtin THX. Which
> in turn has the same color linearity errors as my own calibration. Sigh...
> VT30: Grayscale and gamma can be perfect. Colors - no.
>
> I hope I am wrong.
>
> János, Tóth F. skrev 2012-02-10 15:12:
>
>> I was mad about the VT30E, I said I would never see one of those again
>> after I tried to calibrate one.
>>
>> But interestingly, the G30E is not that bad. The peak error is under
>> dE2000=5, the average is acceptable.
>>
>> VT30 -> Way too much manual controls to achieve effectively nothing or
>> make everything worse. And many manual controls are there to mask the
>> errors in the color calculations (like secondary color adjustments).
>> It's a dead end!
>>
>>
>> 2012/2/10 János, Tóth F.<janos666@xxxxxxxxxx>:
>>>
>>> XYZ and Lab profiles can do that.
>>> But you need to measure a lot of points and there is a big problem
>>> with plasma: Average Brightness Limiter. It rescales the gradient,
>>> causing tonal response and other color fluctuations. You can't correct
>>> for that.
>>> If you profile your display with small windows patterns, those will
>>> measure nicely through the profile evaluation but you will get high
>>> errors with bigger window sizes using the same profile.
>>> It would require a huge and power-hungry 4D LUT processing to correct
>>> for that (built from an insane amount of measurements).
>>>
>>> 2012/2/10 Kristian Jörg<krjg@xxxxxxx>:
>>>>
>>>> I have a question regarding monitor profiling versus calibrating
>>>> HomeTheater
>>>> displays.
>>>>
>>>> When I calibrate my Panasonic VT30 plasma (not connected to a PC) with
>>>> an
>>>> external program i.e ChromaPure I get dE errors in the range of 1.0 or
>>>> less.
>>>> The color calibration is done at 100% stimulus. But when I check the
>>>> color
>>>> balance at 75% stimulus I get errors of about 10 dE! Ouch! There is no
>>>> way
>>>> of correcting that in the TV set's controls even though it has a very
>>>> thorough CMS module.
>>>>
>>>> The question is when profiling a PC display with Argyll (or similar
>>>> profiling software), does it correct color at different levels of
>>>> stimulus
>>>> or only at 100%? I.e if I would us my TV set as a PC monitor would the
>>>> profile correct the color balance from 0-100% stimulus?
>>>>
>>>> --
>>>> Med vänlig hälsning
>>>> Kristian Jörg
>>>>
>>>> Devo IT AB
>>>> Tel: 054 - 22 14 58, 0709 - 15 83 42
>>>> E-post: kristian.jorg@xxxxxxx
>>>> Webb: http://www.devo.se
>>>>
>>>>
>>>>
>
>
>
Other related posts:
