Reference sRGB / Rec.709 Colors
Figure 2a below shows 21 Reference Colors for the
Standard sRGB / Rec.709 Color Gamut as White, Gray, and Black circles.
The 10 Black circles are the 100 percent fully saturated colors on the periphery
of the Gamut triangle.
The 10 Gray circles are the 50 percent saturated colors that are exactly midway
between the White Point and the 100 percent saturated colors on the periphery.
The White circle is the White Point with zero percent color saturation.
Absolute Color Accuracy Error Plots
Figure 2b below shows the measured on-screen colors for the 21 Reference Colors
as displayed on the Kindle Fire HDX 8.9 and iPad Air.
The Nexus 10 is not shown in the Figure because its small Color Gamut
results in very large errors within the plot that are hard to correlate with
its correpsonding Reference Color.
The Reference Colors are all shown as Black circles amd the measured
Chromaticities for the Tablets are shown as Red and Blue circles.
Color Errors smaller than the appropriate JNCD are not visually noticeable.
The 1 JNCD and 3 JNCD are discussed next and appear in both Figures 2a and 2b.
Just Noticeable Color Difference JNCD
The on-screen colors produced by any display can be measured using a
Spectroradiometer together with our DisplayMate Test Patterns.
The accuracy of the colors can then be calculated using the
1976 CIE Uniform Chromaticity color space and compared to the
eye's sensitivity to color.
We present the color accuracy and errors here in terms of
MPCD Minimum Perceptible Color Difference or
JNCD Just Noticeable Color Difference,
where 1 MPCD = 1 JNCD = Δ(u'v') = 0.0040 on the
CIE 1976 Uniform Chromaticity Scale.
Color differences less than 1 JNCD are visually indistinguishable,
while values greater than 1 JNCD are visually noticeable when the
two colors are touching on-screen.
When the colors are not touching and are further apart,
the visual threshold for Just Noticing a Color Difference is higher.
Here we will use 3 JNCD for the threshold of
a visually noticeable display color difference.
Any Color Accuracy or Color Error less than 3 JNCD is visually
The sizes of 1 JNCD and 3 JNCD are shown in Figures 2a and 2b below.