1. Flatness
The surface flatness of the display screen must be within ±1mm to ensure that the displayed image is not distorted. Local bulges or recesses will cause blind spots in the viewing angle of the display screen. The gap between the cabinet and the module and between the module and the module should be within 1mm. If the gap is too large, the borders of the display will be obvious and the screen will be visually uncoordinated. The quality of flatness is mainly determined by the production process.
2. Brightness and viewing angle
The brightness of the indoor full-color screen must be above 800cd/m2, and the brightness of the outdoor full-color screen must be above 5000cd/m2 to ensure the normal operation of the display. Otherwise, the displayed image will be unclear because the brightness is too low. The brightness of the display screen is not the brighter, the better, it should match the brightness of the LED package. Blindly increasing the current to increase brightness will cause the LED to decay too quickly and the life of the display to decrease rapidly. You can ask the manufacturer to provide a parameter report for confirmation. The brightness of the screen is mainly determined by the quality of the LED die.
The viewing angle refers to the maximum angle at which you can see the entire screen content from both sides of the screen. The size of the viewing angle directly determines the audience size of the display screen, so the bigger the better. The viewing angle should be above 150 degrees. The size of the viewing angle is mainly determined by the packaging method of the die.
3. White balance effect
The white balance effect is one of the most important indicators of the display screen. In terms of color science, pure white will appear when the ratio of the three primary colors of red, green and blue is 1:4.6:0.16. If the actual ratio is a little off, there will be a deviation in the white balance. Generally, you should pay attention to whether the white color has a bluish cast. The color is yellowish green. In monochrome, the smaller the brightness difference and wavelength difference between LEDs, the better. There is no color difference or color cast when standing on the side of the screen, and the consistency is better. The quality of white balance is mainly determined by the brightness wavelength ratio of the LED die and the control system of the display screen. The die also affects the color reproduction.
4. Color restoration
Color reproducibility refers to the reproducibility of color by the display screen. That is, the color displayed on the display screen must be highly consistent with the color of the playback source, so as to ensure the reality of the image.
5. Is there any mosaic or dead spot phenomenon?
Mosaic refers to the small squares that appear on the display screen that are always bright or black. It is a phenomenon of module necrosis. The main reason is that the quality of the IC or connector used in the display screen is not up to standard. Dead spots refer to a single point that appears on the display screen that is always bright or always dark. The number of dead spots is mainly determined by the quality of the tube core and whether the manufacturer's anti-static measures are complete.
6. With or without color patches
Color block refers to the obvious color difference between adjacent modules. The color transition is based on the module. The color block phenomenon is mainly caused by poor control system, low gray scale and low scanning frequency.
7. Display stability
Stability refers to the reliable quality of the LED display during the aging stage after it is made into a finished product. You can ask the manufacturer for aging records to determine the conditions that occurred during the aging of the screen.
8. Safety
The LED display screen is composed of multiple boxes. Each box must be grounded for external customer protection, and the grounding resistance should be less than 0.1 ohm. And it can withstand high voltage, 1500V without breakdown for 1 minute. Warning signs and slogans must be placed at the high-voltage input terminal and power supply high-voltage wiring.
9. Packing and shipping
LED displays are valuable goods and weigh a lot, so the packaging method used by the manufacturer is very important. Generally, they are packaged in a single box. Each side of the box must be protected by protective materials to act as a buffer. There is not much room for movement inside the box during transportation. The outer packaging box must be clearly marked.
