Common problem

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  • e-SFR, the ISO 12233-2014 eSFR test standard, the test card pattern is as follows:

    Figure 3.4.1 eSFR test card

    As can be seen from Figure 3.4.1, the eSFR test card has SFR hypotenuse, Tvline hyperbola, grayscale ring, and color block. Therefore, eSFR can measure comprehensive indicators such as resolution (SFR, tvline), dynamic range, and noise. , OECF, color reproduction, etc.

    Find the eSFR thumbnail on the home page of the iQstest software, as shown below:

    Figure 3.4.2 Main interface

    Click on the corresponding thumbnail and the configuration window will pop up:

     eSFR Configuration 
    Figure 3.4.3 eSFR Configuration

    Detailed configuration

    As seen in Figure 3.4.3, eSFR only supports fully automatic testing, ie after importing the image, the software will automatically locate the test image.

    The eSFR configuration consists of three sections:

    1. Display options: With the configuration part of the SFR module, the MTF indicator displayed in the result window can be changed by modifying the MTF unit;

    2. set:

    1) Exposure evaluation --- need to fill in the illumination when shooting the test card;
    2) field of view --- fill in the image height, the distance from the lens to the test card;
    3) standard density parameter ----- the same dynamic range In part, there are three ways to set the density;
    4) Standard color parameters---- Similar to the setting of density parameters, there are three ways to set the standard color;

    3. Optional parameters: Display information about image capture, such as camera, focal length, aperture, shutter, etc., for result output;


    After configuration, click “确认”, the file selection box will pop up, select the eSFR image for testing, the software will automatically locate the image. After the positioning is completed, the preview window will pop up:

    eSFR Automatic positioning preview 
    Figure 3.4.4 Automatic positioning preview

    After confirming that there is no problem with the positioning mark in Figure 3.4.4, you can click the “Start Analysis” button, iQstest will call the module for analysis, and pop up the result, please see the next section.

    Result display

    After the analysis is complete, the results to be presented will pop up automatically:

    eSFR results 
    Figure 3.4.5 eSFR results

    Detailed results

    The eSFR test card has comprehensive functions, including SFR, Tvline, grayscale ring (OECF, noise), and color restoration.

    1) SFR results

    SFR comprehensive results presentation 
    Figure 3.4.6 SFR comprehensive results presentation

    As can be seen from Figure 3.4.6, the MTF50 and MTF30 indicators are given for each analyzable hypotenuse (note, only the unit cycle/pixel is supported here, which will be extended later), which can be calculated by 2 * MTF * PIC Height MTF indicator value of LW/PH unit;

    2) Tvline

    tvline results show 
    Figure 3.4.7 tvline results show

    As can be seen from Figure 3.4.7, the software automatically analyzes all tvlines and gives the corresponding limit resolution. The unit of the limit resolution here is LW/PH.

    3) Gray scale ring

    Grayscale ring results show 
    Figure 3.4.8 Grayscale ring results show

    In Figure 3.4.8, the first chart is the OECF curve, the abscissa is the exposure value, and the ordinate is log(pixel/255). The slope of the fitted line of the curve is the gamma value, which can have linearity on the image. Chemical. The second chart is the standard SNR (signal-to-noise ratio). The higher the signal-to-noise ratio, the better the image quality.

    4) Color reproduction

    Color Restore 
    Figure 3.4.9 Color Restore

    As can be seen from Figure 3.4.9, the color pie chart clearly shows the deviation of the color block pixels from the standard color after the camera is taken, that is, the longer the line segment between the circle and the rectangle, indicating that the camera is less reductive to the color. On the contrary, the more reductive.


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