1. Definition of Color Reproduction
Color reproduction refers to the process by which color film reproduces the colors of a photographic image to closely match the original object through shooting and printing. In digital cameras, it refers to the ability to restore the colors of a photographic image through data processing and computation.
2. Factors Affecting Color Reproduction
Common factors affecting color reproduction include saturation, chromatic aberration, white balance, etc.

White Balance

The basic concept of white balance is to render white objects as white under any light source. In digital cameras, white balance is an image processing technique that compensates for specific colors to restore the captured white object to white, thereby restoring other colors accordingly. Color temperature is a key factor directly affecting white balance. Light sources with different color temperatures require different white balance compensation calculations, making white balance an extremely important step in color reproduction.

Color Temperature

When an object is heated to different temperatures, its radiation changes, exhibiting different corresponding colors. Thus, a connection is established between color and temperature. When the color of light emitted by a light source matches the color of radiation from a black body at a certain temperature, the temperature of the black body can be used to represent the color temperature of the light source, measured in Kelvin (K). A black body is an idealized physical object that absorbs all incident electromagnetic radiation without reflecting or transmitting it, such as the sun. As the color temperature increases, the color of light changes from red to yellow, white, and finally bluish-white.

Saturation

Saturation refers to the vividness of a color, also known as purity. The higher the saturation, the more vivid the color; the lower the saturation, the paler the color, until it appears gray.

Chromatic Aberration

Chromatic aberration, also known as “color fringing” or “purple fringing,” is a common optical issue. It occurs when a lens fails to focus all wavelengths of color onto the same focal plane, resulting in axial chromatic aberration.

If a lens focuses different wavelengths of color at different positions on the same focal plane, chromatic aberration also occurs; this is lateral chromatic aberration.

3. Color Reproduction Testing
3.1 Test Equipment
The test equipment used for color reproduction testing includes the vertical LS-CCXL-2S06-IR Vertical Multi-Color Temperature Fill Light Source and the CP150-R2X Color Test Chart.

3.2 Environment Setup
Switch the chart on the chart holder to the CP150-R2X Color Test Chart. Conduct the test in a dark environment, and adjust the position, direction, color temperature, and illuminance of the vertical multi-color temperature fill light source according to test requirements. Use an illuminance meter to measure and confirm that the illuminance on the chart surface meets the required level.

3.3 Sample Capture
Secure the module with a fixture. Select an appropriate shooting distance based on the module's FOV, and capture test samples under light source color temperatures of 6500K, 4000K, and 2800K, with chart surface illuminances of 800 lux, 200 lux, and 25 lux, respectively.

3.4 RIQA Analysis
(1) Open the RIQA software, select the corresponding module, and choose the corresponding chart type.

(2) Click the “Add +” button to import the image to be tested. Right-click the image to zoom in and view the added image, then click the “Start” button to begin the test.

(3) The “ROI Adjustment” interface appears, showing the default ROI areas. You can adjust the ROI to select the color patches to be tested. Click the “Next” button.

(4) You can fine-tune the position of each ROI selection. After adjusting the ROI selection areas, click the “Analyze” button.

(5) The lower-middle area of the software displays the test results of the captured color chart image, showing the chromaticity angle and Euclidean distance of each color patch relative to the white patch in the color space. Right-click in the upper right corner to view the naming order of the ROI areas. Click the “Generate Report” button.

(6) Navigate to the report generation interface, select the output file format, enter the file name and file path, and click the “Export” button. A prompt will indicate successful report generation once the report is successfully generated.

3.5 Result Interpretation

According to the QC/T 11128 standard requirements for vehicle camera color reproduction testing, the Euclidean distance of the measured chromaticity error between each color patch and the white patch should not be less than 0.02. The hue angle shall meet the following requirements: a) the coordinates of the red patch shall be within the range of (0°, 44.8°) or (332.2°, 360°); b) the coordinates of the green patch shall be within the range of (96.6°, 179.9°); c) the coordinates of the blue patch shall be within the range of (209.9°, 302.2°); d) the coordinates of the yellow patch shall be within the range of (44.8°, 96.6°).

See Also
camera测试用例, 测试用例, 车载感知与显示技术方案