41 Reference Colors for the sRGB / Rec.709 Color Gamut Standard
Most existing consumer content
is based on the sRGB / Rec.709 Color Gamut Standard,
including all 2K Full HD TV content.
Figure 2a
below shows 41 Reference Colors for the
Standard sRGB / Rec.709 Color Gamut as White, Gray, and Black circles.
The 10 Black circles on the outer triangle
are the 100% fully Saturated Colors on the periphery.
The 3 inner sets of Gray triangles are the 25%, 50% and 75% Saturated Colors
between the inner White Point and the 100% Saturated Colors on the periphery.
The White circle is the White Point with 0% Color Saturation.
The colors in
Figure 2a
have been accurately calculated to show the real colors
within the sRGB / Rec.709 Gamut - the colors shown in most published
Color Gamuts are wildly incorrect.
There is a similar set of 41 Reference Colors for the DCI-P3 Color Gamut to
those shown for sRGB / Rec.709 in Figure 2a.
For an in-depth discussion and analysis of these Color Gamuts see this
article.
Note that Complementary Colors lie directly across from one another through the White Point.
The 4 sets of triangles are the 25% 50% 75% and 100% Saturated Colors.
Uniform Color Diagrams
All color measurements are plotted on 1976 CIE Uniform Color Diagrams.
Note that the older 1931 CIE Diagrams that are published by many reviewers
are highly non-uniform and are meaningless for Color Accuracy.
Also the often referenced NTSC Color Gamut is from 1953 and has been
obsolete for over 30 years so stop referencing it!
Absolute Color Accuracy Plots
Cinema Normal Picture Mode:
Figure 2b
below shows the measured on-screen colors for the
sRGB / Rec.709 Reference Colors.
Cinema Wide Picture Mode:
Figure 2c
below shows the measured on-screen colors for the
DCI-P3 Reference Colors.
Reference Colors
The
sRGB / Rec.709 and DCI-P3 Reference Colors
in
Figures 2b-2c
are all shown as Black circles and the measured
Colors for each of the Picture 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 proprietary 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. The 1 JNCD and 3 JNCD sizes are shown in the Figures below. Any Display Color Error less than 3 JNCD on a display is not visually noticeable and appears perfectly accurate to the eye. For an in-depth discussion and analysis of Absolute Color Accuracy see this article.
The Cinema Normal Mode provides a very accurate color match to the sRGB / Rec.709 Color Gamut.
Figure 2c. Cinema Wide Picture Mode Absolute Color Accuracy Plot
The Cinema Wide Mode provides a very accurate match to the standard DCI-P3 Color Gamut.
