2025-06-03
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In commercial displays, stage performances, smart city construction and other scenarios, LED displays are becoming more and more widely used. But in the face of a dazzling array of products on the market, how to judge the quality of an LED screen? This article breaks down 6 core evaluation indicators from a professional perspective to help you avoid blind spots.
First. Flatness: the basic parameter that determines the visual experience
Flatness is one of the important indicators to measure the quality of LED displays. The surface flatness of a high-quality LED display should be within ±1mm, which can ensure that the display image will not be distorted, and local bulges or recesses will cause dead corners in the viewing angle of the display, affecting the viewing experience. The quality of flatness is mainly determined by the production process, and advanced production equipment and strict quality control are the key to ensure flatness.
▍Core indicators: The surface flatness of the display screen should be controlled within ±1mm
1. Importance: Local bumps can cause image distortion and even blind spots (distortion or black screen for marginal viewers).
2. Technical principle: The flatness is determined by the production process, including the module splicing accuracy, box structure design, installation and calibration technology
3. Acceptance skills: Light up the pure white picture, and observe whether there are obvious wavy ups and downs or local depressions at a distance of 3 meters
Second. Brightness and viewing angle: The key parameters of adapting to the scene
Brightness and viewing angle, are also important factors in judging the quality of LED displays. For indoor full-color screens, their brightness should be above 600cd/m², while outdoor full-color screens should be above 4000cd/m² to ensure that images can be displayed clearly in different environments. In addition, the size of the viewing angle directly determines the audience of the display, and generally speaking, the larger the viewing angle, the better. The quality of brightness and viewing angle is mainly determined by the quality of the LED die, which can provide higher brightness and wider viewing angles.
▍Brightness standard (cd/㎡)
4. Indoor screen: ≥600cd/㎡ (to meet the normal viewing of indoor environments such as conference rooms and shopping malls).
5. Outdoor screen: ≥4000cd/㎡ (to cope with direct sunlight scenes, to avoid "whitening and incapacitation" of the picture) Note: The brightness is determined by the luminous efficiency of the LED die
▍ Viewing angle
6. Ideal parameters: 140° ≥ horizontal, 120° ≥ vertical
7. Core Impact: Insufficient angles can cause color distortion when viewed from the side (e.g., dark red, oversaturated blue).
Third. White balance effect: The baseline white balance effect of color reproduction
White balance effcet is an important indicator to measure the color accuracy of LED displays. Ideally, the display should show pure white when the ratio of red, green, and blue primary colors is 1:4.6:0.16. If there is a deviation in the actual proportions, there will be a deviation in white balance, and the common problem is a bluish or yellowish greenish cast. The quality of white balance is mainly determined by the control system of the display, and the die also has an impact on the reproducibility of colors.
▍Golden ratio: RGB three primary colors brightness ratio is 3:6:1
8. Frequently Asked Questions: ▶ Blueish (cool): Not enough green ▶ Yellowish-green (warm): red component is out of balance
9. Detection method: Display a pure white picture to see if it is close to the D65 standard white light (6500K color temperature) to avoid obvious color cast
Fourth. Color reproduction: reject the "filter" display
Color reproduction refers to the LED display to the original image color reproduction ability. A high-quality LED display should be able to accurately reproduce the color of the original image, so that the audience can get a real visual experience. The quality of color reproduction depends not only on the quality of the LED die, but also on the control system and color calibration technology of the display.
▍Key points of evaluation:
1. Skin tone restoration: whether the skin tone is natural when showing the person (avoid blue/redness)
2. Color gamut coverage: whether to support mainstream color spaces such as sRGB/Rec.709 (high-end screens can reach more than 85% of NTSC)
3. Gradient transition: Test the 10%~90% grayscale gradient map to see if the gradient transition is smooth and fault-free
Fifth. Dead Spot and Mosaic: Hard Indicators of Quality Control
When buying LED displays, consumers should also pay attention to checking whether there are mosaics and dead spots. Mosaic refers to the small square that appears on the display that is always bright or black, which is caused by the poor quality of the connectors used in the display. Dead spots refer to a single point on the display that is always on or black, and the number of dead spots is mainly determined by the quality of the die. These defects will seriously affect the display effect and service life of the display.
▍ Dead spot
4. Definition: A single pixel that is always on (bright spot) or always dark (dark point).
5. Eligibility criteria: Dead spot rate≤ 0.0001% (i.e. ≤ 1 dead spot out of 1 million pixels).
6. Causes: Defective core, soldering or poor packaging process
▍Mosaic
7. Definition: A solid/dark area (≥2×2 pixels) consisting of multiple adjacent pixels
8. Core causes: poor contact of module connectors and failure of driver chips
9. Detection method: display monochrome (red/green/blue/white) in full screen, and check for abnormal points with the naked eye
Sixth. Color block phenomenon: The color block phenomenon of the short board of the exposure control system
refers to the obvious color difference between adjacent modules, and the color transition is based on the module. The color patching phenomenon is usually caused by the display's poor control system, low gray scale, or low scanning frequency. The phenomenon of color blocking can cause images to look choppy and degrade the visual experience.
▍Performance characteristics: There is obvious color difference between adjacent modules, forming a "patch" display
10. Technical Bottlenecks:
1. Insufficient gray level (color level fault is easy to occur when ≤ 12bit)
2. Low scanning frequency (< 1920Hz with color patch ghosting in the movie)
3. Poor brightness consistency (module brightness deviation >5%)
