Reference sRGB / Rec.709 Colors
Virtually all current consumer content
is based on the sRGB/Rec.709 Color Gamut Standard.
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.
All figures are plotted on a CIE 1976 Uniform Color Diagram.
Note that the older 1931 CIE Diagrams that are frequently published
are highly non-uniform and meaningless for Color Accuracy.
A similar set of Adobe RGB Reference Colors is shown below
in Figure 2d for the Professional Photo Mode.
Absolute Color Accuracy Plots
Cinema Mode:
Figure 2b
below shows the measured on-screen colors for the
sRGB/Rec.709 Reference Colors.
Adapt Display Mode:
Figure 2c
below shows the measured on-screen colors for the
sRGB/Rec.709 Reference Colors.
Professional Photo Mode:
Figure 2d
below shows the measured on-screen colors for the
Adobe RGB Reference Colors.
The Reference Colors in Figures 2b-2d are all shown as Black circles and the measured Colors for each of the Screen Modes are shown as Red circles. Color Errors smaller than the appropriate JNCD are not visually noticeable. The 1 JNCD and 3 JNCD Errors are discussed next and are shown in the Figures below.
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 Display Color Error less than 3 JNCD is not visually noticeable and appears perfectly accurate to the eye.
The 1 JNCD and 3 JNCD sizes are shown in the Figures below.
Note that Complementary Colors lie directly across from one another through the White Point.
The 50% Saturated Colors are midway between White and the 100% Saturated Colors.
Figure 2b. Cinema Mode Absolute Color Accuracy Plots
The Cinema Mode provides an accurate color match to the Standard sRGB/Rec.709 Gamut.
Figure 2c. Adapt Display Mode Absolute Color Accuracy Plots
The Adapt Display Mode has colors that are more saturated than the sRGB / Rec.709 Gamut.
Thin red lines outline the larger Adapt Display Gamut for the 50% and 100% Saturated Colors.
Thin black lines pair up the Reference Colors with the measured Adapt Display Mode colors.
Figure 2d. Professional Photo Mode Absolute Color Accuracy Plots
The Professional Photo Mode provides an accurate color match to the Adobe RGB Gamut.
