9 tips to easily choose LED screens. Have you mastered them?

Maximum brightness

Refers to the brightness of each primary color of the LED display at the highest gray level and highest brightness under a certain ambient illumination. In short, it is the brightness measured in the normal direction using a light gun when the display is set to white level 255 using software.

For outdoor LED displays, there are different requirements for maximum brightness depending on the environment in which they are used. Because in situations where the ambient light is relatively strong, the brightness of the LED display is required to be higher so that the public can clearly see the content displayed on the screen. Generally speaking, displays facing south have lower maximum brightness requirements, as long as it reaches 4000CD/m2 to meet the requirements, while displays facing south require the entire screen brightness to reach 7000CD/m2. The requirements for east-facing, west-facing and south-facing are the same, because sunlight will directly shine on the LED display part of the time. Theoretically, a brightness requirement of greater than 5500 CD square meters is sufficient.

Color temperature

When we see the color of the image on the display screen inconsistent with or different from the material, our picture will be seriously distorted. This is related to the color temperature of the LED display screen. If the human eye directly views the display screen, its white level will be different. The color temperature value is between 6500 and 8000K. If it is a display screen used by a TV station for broadcast, the actual color temperature of the screen needs to be adjusted to about 5500K, so that the picture on the display screen will be real after being recorded and broadcast by the camera.

Refresh rate

The refresh rate refers to the number of times the LED display information is displayed completely per second. If the refresh frequency is too low, the LED display will jitter when viewed by the human eye. Usually we will see scanning lines when shooting with a camera. Generally, the human eye requires a refresh frequency of 300Hz or above. That is, as long as the refresh rate exceeds 300Hz, the LED display will not feel jittery when viewed with the naked eye. If you use a camera to shoot, depending on the different settings of different cameras, generally at least 600Hz or above is required to capture no scanning lines.

High refresh rate can improve the brightness and color fidelity of the display. It can be detected with a digital camera. If the refresh rate is high, the picture taken by the camera will be very clear, without snowflakes or scanning lines. This indicator is especially important when renting screens and television broadcasts.

Wavelength

Wavelength determines whether the color is pure and consistent. The identification method is very simple; if you don’t have professional equipment, how can you identify it with your eyes?

First: the entire screen is printed in white. The screen should be pure white without any other noise. If you think it's a little reddish or bluish, it means there's something wrong with the display material and process quality control. If used for a long time, it will become more and more serious.

Second: When printing single colors of red, green, and blue, the color of the central wavelength is what we usually call true blue, red, and green. If the color is darker or lighter, it proves to be a biased wavelength. If a certain color is inconsistent, it proves that the wave difference is too large. For a high-quality display, within the range of the central wavelength, the blue-green wave difference is controlled at 3nm, and the red wave difference is less than 5nm.

The perspective of the luminous tube

The light-emitting viewing angle of a light-emitting tube refers to the angle formed by the two viewing directions on the same plane and the normal direction when the brightness in the viewing direction drops to half of the brightness in the normal direction of the LED display. Divided into horizontal viewing angle and vertical viewing angle.

For outdoor LED advertising displays, elliptical light-emitting tubes or SMD light-emitting tubes are generally used. Elliptical light-emitting tubes have the characteristics of small angles and high brightness. The vertical viewing angle of SMD light-emitting tubes is much larger than that of elliptical tubes, but their brightness is smaller than that of elliptical light-emitting tubes. From the user's perspective, light-emitting tubes with different viewing angles should be selected according to the audience area of ​​the LED display and the surrounding light environment.

For indoor LED displays, due to their low brightness requirements and generally wide audience, SMD light-emitting tubes are the best choice. It should be noted that in order to reduce costs and confuse users, some manufacturers of light-emitting tubes in the market now make the brightness of the light-emitting tubes higher and the viewing angles smaller than those of conventional light-emitting tubes. This will cause the LED display to be very bright when viewed from the front, but the image cannot be seen clearly when viewed from a relatively large angle from the side.

In order to increase the brightness, small-sized LED chips are usually packaged at a small angle. Large sizes do not require small-angle packaging because they do not require such high brightness. Therefore, large angle (110), high brightness and low current are the best.

Circuit design part

The design and materials of the circuit board play a vital role in the stability and display effect of the LED display. There are mainly the following requirements:

1. Material requirements: PCB board thickness, generally 1.6mm thickness; Material: FR-4 glass fiber board, some manufacturers may use FR-2 paper substrate in order to reduce costs; Copper foil thickness: The thickness of the copper foil affects the heat dissipation and wiring of the PCB board The stability of PCB plays an important role that cannot be ignored. The normal copper foil thickness is 35um (1Oz), and some manufacturers will use 18um (0.5Oz) copper foil thickness to pass off the quality. So how do you identify it as a consumer? You can take an empty PCB to distinguish it by weight. Under normal circumstances, the heavier the better.

2. Several key points in design: connectors. Connectors refer to the connections between modules. There are two main types that are commonly used in the market, one is horns and the other is pin headers. The advantage of horns is that they can hold the cable through two clamping positions, making it less likely to cause malfunctions caused by connector problems. Regarding the choice of electrolytic capacitors and tantalum capacitors, tantalum capacitors are undoubtedly the first choice when long life is required, and electrolytic capacitors are the first choice when low price is required.

Automated production equipment

Most of the LED displays are electronic components, and static electricity is very harmful to electronic components. Sometimes static electricity directly breaks down components and damages them. Sometimes it does not break down directly, but leaves hidden dangers. The side effect is that the components are damaged after being used for a period of time. In the electronics manufacturing industry, people have thought of many ways to deal with artificial static electricity, including wearing static rings, wearing static clothes, using dust-free workshops, etc. In fact, the most effective way is to avoid human hands touching electronic components as much as possible, and the use of automated equipment achieves this goal.

Average power consumption

Square power consumption refers to the power consumption generated by an LED display with an area of ​​one square meter. The unit of power we usually talk about is watts/hour. For example, the power consumption of a square meter of LED display is 300 watts, so the display will consume 300 watts/hour per square meter per hour, which is what we often call 0.3 kilowatt-hours of electricity. The power consumption of LED displays generally has two indicators, one is the maximum power consumption, and the other is the usage power consumption. The maximum power consumption refers to the power consumption when the LED display screen is at its maximum brightness. How can you tell the maximum power consumption with your eyes?

The method is very simple: look at the number of power supplies behind the cabinet, multiply it by the maximum power of each power supply, and calculate the maximum power consumption per square meter based on the size of the cabinet. There are two commonly used power supplies, 200W and 300W power supplies.

Indoor small spacing: low brightness and high gray

Low brightness and high gray, the specific explanation is: when the brightness range of the small spacing LED display is in the range of 100 cd/O-300 cd/O, the grayscale of the display screen is not lost, or the degree of grayscale loss is within a range that is difficult for the human eye to detect.

Low brightness and high gray will be one of the key factors that distinguish the quality of small-pitch LED display products. For small-pitch products, the competition between LED display screens will no longer be about who has higher brightness, but about who has lower brightness. I am comparing whose display screen can reduce the brightness without losing the gray scale and image quality. In other words, only small-pitch LED displays with low brightness and high gray are good products that meet user requirements and have competitive strength.

When human eyes stare at high-brightness small-pitch LED displays at close range and for a long time in a dark indoor environment, the unique high brightness of LEDs often makes people feel dazzling, and even causes eye soreness, tears, and reduced vision. Therefore, if the brightness of the LED display is too high, it will cause visual fatigue to users of indoor applications, and may even cause serious irreparable damage to the human eyes! It can be said that the brightness of small-pitch LED displays is definitely not as high as possible, and its brightness must be reduced. A large number of tests have shown that the brightness range of the LED display is controlled within the brightness range of 100 cd/O-300 cd/O, which is relatively comfortable for the human eye.

But this problem cannot be solved by directly adjusting the brightness of the display. Because conventional LED displays have the characteristics of low brightness and low gray, which means that when the brightness of the display decreases, it will be accompanied by a loss of grayscale.