How to accurately test the brightness of the display and precautions

     Many customers are asking how to test the brightness of the display. Here is a brief introduction. Testing the brightness of the liquid crystal screen (LCD) needs to be combined with specific needs (such as professional testing or daily verification). The following is an explanation from two scenarios: professional laboratory testing and daily simple testing, covering tool selection, operation steps and precautions:

1. Core tools

· Brightness meter/photometer: Professional equipment (such as Konica Minolta CS-2000, Topcon BM-7A), which can accurately measure the surface brightness of the screen (unit: nit, nit), with an error of usually <1%.

· Spectroradiometer (optional): If you need to analyze color (such as HDR color gamut coverage), you can choose a spectroscopic device (such as Photo Research PR-655) to measure brightness and spectral characteristics at the same time.

· Darkroom/shading environment: To avoid interference from ambient light, it needs to be carried out in a darkroom (or use a hood to completely cover the screen).

· Test software: With the screen driver tool (such as DisplayCAL, X-Rite i1Profiler), the screen can be controlled to display specific test patterns (pure black, pure white, grayscale bars, etc.).

2. Test steps

Step 1: Environmental preparation

Turn off all ambient light sources to ensure that there is no stray light in the test area; the screen is clean and dust-free (avoid local occlusion affecting the measurement).

Step 2: Equipment calibration

· Turn on the luminance meter to warm up (usually 10-15 minutes), and use a standard white board (such as a NIST-calibrated white board) to calibrate the instrument to ensure that the measurement benchmark is accurate.

· Connect the test software, set the screen resolution and refresh rate to standard values (such as 1920×1080@60Hz), and turn off dynamic contrast, local dimming and other functions (to avoid interference from dynamic brightness adjustment).

Step 3: Basic brightness measurement

· Peak brightness: The screen displays pure white (RGB=255,255,255), aim the brightness meter at the center of the screen (or cover the entire screen as required by the standard), and read the maximum brightness value (HDR screens need to verify whether they can reach the nominal value, such as 1000nit).

· Uniformity test: Under a pure white screen, take the center of the screen as the origin, measure the brightness values of multiple positions (such as 9 points, 25 points) according to the grid method (such as taking points every 10% width/height), and calculate the maximum deviation (industry standards usually require ≤10%).

· Grayscale brightness: Display different gray levels (such as 0-255 levels), measure the brightness value of each gray level, and verify whether it complies with the linear or gamma curve (such as sRGB standard).

Step 4: Dynamic brightness verification (optional)

If the screen supports local dimming (such as Mini-LED), it is necessary to test the brightness difference in different areas (such as the bright/dark areas of HDR content) to verify whether there is a "halo" (Blooming) phenomenon.

Notes

1. Ambient light interference: Professional testing requires strict light shielding, and daily testing avoids strong light directly hitting the screen (such as sunlight, ceiling lights), otherwise it will affect perception and device measurement.

2. Screen status: Let the screen warm up for 30 minutes before testing (LCD backlight needs time to stabilize) to avoid low brightness during cold start.

3. Setting impact: Turn off "Auto Brightness", otherwise changes in ambient light will cause automatic brightness adjustment and interfere with testing.

4. Local dimming limit: When a screen with local dimming (such as Mini-LED) displays high-contrast content, the dark area may actively reduce the brightness. At this time, the measured dark brightness will be lower than the global brightness, which is a normal design.

     Shenzhen Hongjia has been professionally engaged in R&D, production and sales of 1.14-inch to 12.1-inch display screens and supporting touch screens for 12 years. We serve many Fortune 500 companies and provide 36 months of after-sales service. We have a professional display brightness measurement instrument BM-7. The display brightness can reach 2000 lumens, meeting the requirements of clear readability in the sun. It is widely used in drone remote controls, handheld devices, aerospace equipment and other products. Customers are welcome to email us for consultation.