[argyllcms] Re: Monitor screen color unevenness/irregularity

  • From: János, Tóth F. <janos666@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 16 Apr 2012 20:08:19 +0200

These are CCT and Y measurements on a NEC PA231W with the uniformity
compensation set to 0 and 5 (off, max):

img802.imageshack.us/img802/7595/pa231whomogeneitycomp.jpg

But you obviously loose a lot from the contrast ratio of you use this feature.

2012/4/16, Graeme Gill <graeme@xxxxxxxxxxxxx>:
> Alexey Blinov wrote:
>> I measured color on different places on a fully white screen. When
>> visualized on the CIE 1931
>> x,y plane, I got an area of size around 0.01. The distance between two
>> closest shades of white
>> (255,255,255 and 254,255,255) is around 8e-4. Accuracy of the colorimeter,
>> i.e. the diameter of
>> the smallest circle enclosing many measurements of same color at same
>> place, is around 4e-4.
>>
>> So, variations of color on the screen is around 10 times more than the
>> variation due to limited
>> (8-bit per channel) digital representation. Who measured such unevenness
>> of professional
>> monitors, could you post your results?
>
> Hi,
>       spatial color unevenness in screens is a quite well known display 
> defect.
> One of
> the specifications of higher quality screens is improved spatial screen
> uniformity,
> and many of these displays take technical measures to ensure uniformity,
> such
> as spatial calibration systems.
>
> (I'm not sure x,y values are a good way of evaluating non-uniformity, since
> they
>  do not correlate to visual differences. Delta E is a better measure in this
> regard.)
>
> There are various industry standard methods and thresholds for display
> uniformity
> measurement, such as VESA and ISO standards.
>
> Graeme Gill.
>
>

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