Color reproduction (Colour rendering) refers to the ability of a Camera Monitor System (CMS) to accurately reproduce the original colors of a target chart on the display.

Metrics (ISO 16505 6.8.3):
For color reproduction, the hue angles of the reproduced colors of the chart patches on the display shall meet the following requirements. The color coordinates are described based on the CIE 1976 color space:
— The coordinates of the red patch shall not exceed the range of [0°, 44.8°] or [332.2°, 360°];
— The coordinates of the green patch shall not exceed the range of [96.6°, 179.9°];
— The coordinates of the blue patch shall not exceed the range of [209.9°, 302.2°];
— The coordinates of the yellow patch shall not exceed the range of [44.8°, 96.6°];
— To ensure distinguishability from the white patch, the distance to white is limited to Ri ≥ 0.02, where Ri is the chromaticity distance of each patch (i = red, green, blue, yellow) relative to white (i = white).
For the reproduction of signal lights, the yellow light shall be identifiable as yellow, the blue light as blue, and the red light as red.

Calculation Principle (ISO 16505 7.8.3):
Taking the color coordinates of the reproduced reference white patch on the CMS display $(u'_r, v'_r)$ as the reference, first obtain the color coordinates of the target patch (i = R, G, B, Ye) on the display $(u'_{it}, v'_{it})$, and calculate the difference in color coordinates between the two $(\Delta u' = u'_{it} - u'_r, \Delta v' = v'_{it} - v'_r)$; then, based on the quadrant in which this difference lies, obtain the chromaticity angle $\theta_{icolor}$ of the target patch relative to the reference white using the corresponding arctangent formula with angle compensation:
Quadrant 1 $\left( (u'_{it} - u'_r) \geq 0 \text{ and } (v'_{it} - v'_r) \geq 0 \right): \theta_{icolor} = \arctan\left( \frac{v'_{it}-v'_r}{u'_{it}-u'_r} \right)$
Quadrant 2 $\left( (u'_{it} - u'_r) < 0 \text{ and } (v'_{it} - v'_r) \geq 0 \right): \theta_{icolor} = 180^\circ + \arctan\left( \frac{v'_{it}-v'_r}{u'_{it}-u'_r} \right)$
Quadrant 3 $\left( (u'_{it} - u'_r) < 0 \text{ and } (v'_{it} - v'_r) < 0 \right): \theta_{icolor} = 180^\circ + \arctan\left( \frac{v'_{it}-v'_r}{u'_{it}-u'_r} \right)$
Quadrant 4 $\left( (u'_{it} - u'_r) \geq 0 \text{ and } (v'_{it} - v'_r) < 0 \right): \theta_{icolor} = 360^\circ + \arctan\left( \frac{v'_{it}-v'_r}{u'_{it}-u'_r} \right)$
To confirm that the reproduced patches (i = R, G, B, Ye) on the display can be separated from the neutral white patch, measure the Euclidean distance between each tested patch “i” and the white patch (i = white) for verification: $R_i = \sqrt{(u'_{it} - u'_r)^2 + (v'_{it} - v'_r)^2}$

Method (ISO 16505 7.8.3):
Based on the color reproduction test chart, use an imaging luminance meter to capture the display screen, and measure the color coordinates of each individual patch, as well as the chromaticity angle and Euclidean distance from each patch to the reference white patch, to quantify the color reproduction capability of the CMS.
Test setup is shown in the following figure:
Test environment:
Camera side:
1. Adjust the position of the light source and the relative distance between the camera under test (DUT) and the test chart to ensure that there is no direct reflected light or direct incident light from the light source to the camera lens;
2. The light source must be similar to the CIE D65 standard illuminant, with a color temperature of TC = 6500K and a permissible tolerance of ±1500K;
3. The entire image area of the camera should be covered by the chart image to avoid interference from unknown background images or other light sources.

Display side:
1. Adjust the display and the imaging luminance meter so that the luminance meter is aimed at the center of the display and its optical axis is perpendicular to the display;
2. Use the imaging luminance meter to capture the display screen.

Test chart:
- Use a test chart based on the X-Rite “ColorChecker” chart or an equivalent chart with eight colors (R, G, B, Ye, Cy, Mg, black, and white);
- The patches must be arranged at a uniform distance from the center of the image;
- The arrangement order of the patches must place complementary colors in opposite positions;
- The background shall be neutral gray with a diffuse reflectance ρ of approximately 18%;
- Charts that are aged or excessively exposed to sunlight/UV light must be replaced in a timely manner.

Camera settings:
Auto white balance: Measurement shall begin immediately after the camera completes the auto white balance operation. If there is a neutral gray deviation after auto white balance, the deviation value and convergence instability must be reported.
Manual white balance: If manual white balance is used, the camera should be pre-adjusted using a neutral white chart before measuring the color reproduction chart.

Solutions:
Automated Chart Switching Mount Test System Enables chart support and automatic switching, supports storage of 10 charts, and accommodates a maximum size of 1600*1000mm. The frame surface is treated with an anti-reflective coating to avoid interference from test reflections.

CMS Color Test Chart Complies with the ISO 16505 standard and is suitable for CMS color reproduction testing.

Multi-CCT LED Fill Light Source (Visible and NIR) Provides highly uniform illumination for reflective test targets and can simulate complex test environments.

6-Axis Programmable Stage Supports XYZ 3-axis linear displacement and 3-axis rotation, offering high flexibility for camera position and orientation adjustment and support.

Display and Luminance Meter Mobile Mount Supports the screen, light source, and 2D luminance meter; allows adjustment of the screen to an appropriate angle.

2D Imaging Luminance Meter

RIQA-CMS Image Quality Analysis Software Designed specifically for automotive Camera Monitor Systems (CMS), it is the world's first image analysis software developed entirely for international and domestic CMS standards such as ISO 16505, UN R46, and GB 15084.
The color analysis result output of the RIQA-CMS image quality analysis software is as follows: