1. Concept of Texture

In the field of digital imaging, texture generally refers to low-contrast details. For example, the leaves on a tree or each blade of grass in a prairie are details, also known as texture. In principle, a camera should be able to reproduce these details. For a camera, distinguishing texture from unwanted noise in low-light scenarios where higher ISO sensitivities are used is extremely challenging. Therefore, noise reduction processing on images often leads to texture loss.

2. Concept of Texture Loss

Texture loss refers to the loss of some high-frequency information in an image at dense textures. Simply put, it means the image loses details due to noise reduction, as shown in Figure 2. Today's advanced image processing techniques can reduce noise and other artifacts, but in the process, texture is also reduced, resulting in poorer image quality.

To strike a balance between noise reduction and texture loss, both noise and texture loss need to be quantitatively analyzed.

3. Testing for Texture Loss

From a technical perspective, the measurement method for texture loss is essentially a measurement of resolution. Low-contrast Siemens star charts and dead leaves charts can be used for testing. However, since the dead leaves chart more closely resembles natural scenes, using it to measure texture loss is more aligned with real-world conditions. Therefore, the dead leaves chart is used here to test for texture loss.

Laboratory Test Environment Setup:

1. Test charts: B&W Dead Leaves Chart IMC064 / Color Dead Leaves Chart IMC071 / Color Dead Leaves Chart CP142-R2X / B&W Dead Leaves Chart CP316-R2X;

2. Test environment: Currently, shooting is performed in a dark environment, i.e., with the lights off;
3. Test equipment: Camera module, image capture card, fill light, chart stand, illuminance meter, height-adjustable table, image capture software, RIQA analysis software, fixture.

Test Procedure:

(1) Switch the chart stand to the gray card, and attach the B&W or color dead leaves chart to the gray card;

(2) Turn off the lights to create a dark environment, turn on the fill light, adjust the color temperature and brightness level, and use the illuminance meter to measure the illuminance at the top, bottom, left, right, and center of the chart to reach the required illuminance;

(3) Capture the image and save it in the desired format.

Analysis Procedure (taking the B&W Dead Leaves Chart IMC064 as an example):

(1) Open the RIQA software, click “Texture” in the “Resolution” module, select the chart type as “TE265”, click “Add”, and add the corresponding images to be analyzed;
(2) Click “Start”, select the area to be analyzed, and click “Next”; (3) Click “Next” to precisely frame the analysis area;

(4) Click “Analyze”, then click “Generate Report”, enter the report name, storage path, and report type, and click “Export” to view the report at this path.

4. Result Analysis:
For texture loss, we primarily focus on the MTF50P value.

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camera测试用例、测试用例、riqa简介