- What is a LED Screen?
A LED screen is a video display which uses light-emitting diodes. An LED panel is a small display, or a component of a larger display or screen. They are typically used outdoors in store signs and billboards, and in recent years have also become commonly used in destination signs on public transport vehicles. LED panels are sometimes used as form of lighting, for the purpose of general illumination, task lighting, or even stage lighting rather than display.
Types of LED Screens
There are two types of LED panels: conventional (using discrete LEDs) and surface-mounted device (SMD) panels. Most outdoor screens and some indoor screens are built around discrete LEDs, also known as individually mounted LEDs. A cluster of red, green, and blue diodes is driven together to form a full-color pixel, usually square in shape. These pixels are spaced evenly apart and are measured from center to center for absolute pixel resolution. The largest LED display in the world is over 1,500 foot (457.2 m) long and is located in Las Vegas, Nevada covering the Fremont Street Experience. The largest LED television in the world, the Center Hung Video Display at Cowboys Stadium, is 160 by 72 feet (49 by 22 m), 11,520-square-foot (1,070 m2).
Most indoor screens on the market are built using SMD technology—a trend that is now extending to the outdoor market. An SMD pixel consists of red, green, and blue diodes mounted on a chipset, which is then mounted on the driver PC board. The individual diodes are smaller than a pinhead and are set very close together. The difference is that the maximum viewing distance is reduced by 25% from the discrete diode screen with the same resolution.
Indoor use generally requires a screen that is based on SMD technology and has a minimum brightness of 600 candelas per square meter (cd/m², sometimes informally called nits). This will usually be more than sufficient for corporate and retail applications, but under high ambient-brightness conditions, higher brightness may be required for visibility. Fashion and auto shows are two examples of high-brightness stage lighting that may require higher LED brightness. Conversely, when a screen may appear in a shot on a television studio set, the requirement will often be for lower brightness levels with lower color temperatures (common displays have a white point of 6500 to 9000 K, which is much bluer than the common lighting on a television production set).
For outdoor use, at least 2,000 cd/m² is required for most situations, whereas higher-brightness types of up to 5,000 cd/m² cope even better with direct sunlight on the screen. (The brightness of LED panels can be reduced from the designed maximum, if required.)
Suitable locations for large display panels are identified by factors such as line of sight, local authority planning requirements (if the installation is to become semi-permanent), vehicular access (trucks carrying the screen, truck-mounted screens, or cranes), cable runs for power and video (accounting for both distance and health and safety requirements), power, suitability of the ground for the location of the screen (if there are no pipes, shallow drains, caves, or tunnels that may not be able to support heavy loads), and overhead obstructions.
- What is the difference between real pixel LED screens and virtual pixel LED screens?
With the virtual pixel technology, the LED display will appear a more clear vision. Theoretically the resolution will be 4 times of a real pixel technology LED display.The difference of a real a virtual pixel LED screen of LED display can be seen in the next pictures.
Virtual Pixel LED Screen Real Pixel LED Screen
How do virtual LED screens work?Below you can clearly see how the virtual pixels are made, we surely recommend you a virtual display, even so new technology of Dot Matrix it’s still better than virtual pixels, because the three colors RGB are in the same dot or pixel, just like the SMD technology and also the Dot Matrix have a horizontal viewing angle of over 160 degrees. The virtual pixel LED screens have a horizontal viewing angle of upto 130 degrees.
- LED Screens and Refresh Rate
What is the refresh rate for LED screens?
The refresh rate of a LED screen is the number of times in a second that the LED screen hardware draws the data. This is distinct from the measure of frame rate in that the refresh rate for LED screens includes the repeated drawing of identical frames, while frame rate measures how often a video source can feed an entire frame of new data to a display.
For example, most movie projectors advance from one frame to the next one 24 times each second. But each frame is illuminated two or three times before the next frame is projected using a shutter in front of its lamp. As a result, the movie projector runs at 24 frames per second, but has a 48 or 72 Hz refresh rate.
Increase refresh rate for decreasing LED screen flickering
On LED screens, increasing the refresh rate decreases flickering, thereby reducing eye strain. However, if a refresh rate is specified that is beyond what is recommended for the LED screen, damage to the display can occur.
Normally LED screens have a refresh rate of over 300Hz, which is more than 5 times the refresh rate of a normal cathode television which is 50Hz (PAL and SECAM) or 60Hz (NTSC). For football stadiums (stadium LED screens and perimeter LED screens) LED screens can reach a refresh rate of over 800Hz, which means that they won´t show any flickering when recorded with a video camera and broadcasted live on television.
- Life Time of LED Screens
What is the life time for LED screens?
The life time for LED screens is over 100,000 hours, but it depends how the client is taking care of his LED screen and how it is used. When a LED Screens´ life time will get to 100,000 hours, it means that the brightness of the LED´s of the LED screen is about 50% of it´s original brightness, depending on several factors that will enlarge a LED screen´s life time or reach 100,000 hours.
The most important factors are, which are:
LED Screen Maintenance
LED Screen Temperature
LED Screen Power Protection
LED Chip Packaging
LED Screen Maintenance
Maintenance is a very important factor, dusty environments require more often maintenance to the LED screen than clean environments. The soldering of the LED chips can dry out and break which require changing often pieces like LED modules and receiving cards.
LED Screen Temperature
The temperature of the LED screen is very important to keep it cool. In hot environments it is wise to install a cooling system inside the LED screen to avoid overheating.
LED Screen Power Protection
Electrical peaks can put more force on the electrical components which will decrease life time. It is wise to install a protection that can control the peaks.
LED Chip Packaging
The LED chip packaging material is also a very important variable that will determine the lifetime of a LED screen. For example iron has less life than cuprum LED packages. Besides iron is more corrosive than cuprum.
- What do the IP protection grades for LED screens mean?
LED screens must be able to work 24 hours a day and 7 days a week and withstand extremely stormy or sandy storm weather. For manufacturers it is required that the LED screens meet the criterion for outdoor LED screens IP65, and for indoor LED screens IP20. So what do these criterion mean? And what does IP65 and IP20 stand for?
LED Screen IP RatingThe IP code (or International Protection Rating, sometimes also interpreted as Ingress Protection Rating) consists of the letters IP followed by two digits and an optional letter.
As defined in international standard IEC 60529, it classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures of the LED display screens. The standard aims to provide users more detailed information than vague marketing terms such as waterproof.
International Protection Rating Of LED Screens for Outdoor LED Display
It’s the technical introduction by reading which you will command all the conception in details. But here as a company dedicated in LED display screens, we’d like to be short to avoid any unnecessary mistake.
Front Outdoor LED Screens: IP67
The first digit indicates the protection against dust. And “6” means Dust Tight, which means no ingress of dust and complete protection against contact. The second digit indicates the protection against liquids. And “7” means ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 m of submersion).
Back Outdoor LED Screens: IP55
The 2 digits indicate the same parameter with above. But the letters are different. And the first “5” means Dust Protected: Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment; complete protection against contact. The second “5” means: Water projected by a nozzle against enclosure from any direction shall have no harmful effects.
According to the “The General Criterion For LED Displays”: Indoor LED displays should be IP20+, Outdoor LED displays should be IP33+ So with IP67 for the front side, and IP55 for the rear side, we ensure the led display working well in all the outdoor environment and weather conditions.
Clarify On the IP65 LED Screens
Sometimes clients are misled by non-professional suppliers who aim only selling out the led screens. As the reliable partner, we think it’s necessary to make clear each confusing point, and be honest with true result. For the front side, it’s no difficult to reach “IP65”. But for the rear side, as long as there’s air inlet and outlet, the protection against dust can’t reach “6” – totally prevent the dust. In another words, as long as the heat dissipation design based on fans, the air inlet and outlet is necessary. As a result, the ingress protection can’t reach “6”.
LED Screens LED Display Test Method of “IP_5”
The inside diameter of water jet: 6.3mm
Distance between the display and water jet: 2.5-3m
Flow velocity: 12.5 L/min ±5%
Test Time: 3 min/m2
Test Condition: Every feasible angle jet onto the test sample cabinets.
- Relationship between pixel pitch distance and viewing distance
According to the working environment, LED displays can be divided into indoor led screens, outdoor led screens and semi-outdoor led screens. There are some data in theory which can reflect the relationship between the pixel pitch and the best viewing distance. The relationship between pixel pitch distance and the best viewing distance Pixel Pitch P5 P6 P7.62 P8 P10 P12 P16 P20 P25 Viewing Distance (m) 11 14 17 18 23.5 28.2 35.5 46.99 56.4 Viewing Distance (ft) 36 46 56 59 77 92.5 116.5 154.16 185
In the actual application, because of the limitation of led display installation environment and identify ability, led display’s smallest viewing distance is mean the shortest distance that can identify the text and picture showing. The shortest viewing distance and led specification are on below:
The smallest viewing distance and led display specification Viewing Distance (m) 3 ~ 5 5 ~ 8 8 ~ 10 10 ~ 12 12 ~ 16 16 ~ 20 20 ~ 25 > 25 Viewing Distance (ft) 10 ~ 16 16 ~ 26 26 ~ 33 33 ~ 39 39 ~ 52 39 ~ 66 66 ~ 82 > 82 Pixel Pitch P3
- The Effective Control Distance Of LED Displays and LED Screens
In this article, we will explain the effective control distance of full color LED displays and LED screens signals transferred with a normal network cable. Generally, the signal cable of a LED display is RJ45 which is a standard network cable. The control distance can reach up to 100m, which is enough for most clients needS. A LED screen will be installed with a structure, the function of which is not only to back up the LED display and decoration, but also, there will be a small control room inside the LED screen structure or nearby the LED screen structure where a PC will be placed to control the LED screen.
Economic LED Screen Controlling
The most economic way for controlling a LED screen is using the basic RJ45 signal cable. But for some special clients, they will not place the control PC nearby the LED display, because it’s not convenient for them to edit and program the content nearby the LED display. Those clients will request for a longer control distance. In this condition, a fibre-optic solution will be chosen. And in this way, the control distance from the LED screen to control room where the controlling computer is placed can reach up to 10Km, or even more. This will bring a relative high cost which won’t make it an economic solution.
Usually for LED screens and LED displays that will be controlled over a long distance, an internet connection can be choosen too. This only applies if an internet connection is available for both locations to control the LED display and to control the PC. We recomment to control the LED screen remotely by the internet of course.
LED Displays Controlling Remotely
For most application, the signal from the controlling PC to the LED display screen is transferred via a RJ45 cable. The distance of 100m is normally far than enough for most clients enough for most clients’ requirements and most economic way. But some clients would like to control the display in a further distance than 100m, or even thousands of Km. For these cases the remote control by internet will be chosen.
For to realize controlling remotely the LED screen by internet you need the following:
The internet connection ror both locations, for the LED screen as well as for the controlling PC;
Two PC’s, one for to place at the LED screen and the other one to control the LED screen remotely.
At last, we will introduce the signal transfer in a simple way. For most people it’s not strange to know that one PC can control another PC through internet. And the essential of LED display remote control is the same. But software will combine and set the control in a convenient method. And the operator will easily control the display from quite a far distance.
- Refresh Rate and Frame-Changing Frequency of LED Displays
A LED display screen is a full digital equipment which is driven by the impulse current. The Gray-scale and Brightness is realized by PWM (pulse-width-modulation) and the illumination of a LED is a pulse-type. When the frequency of pulse repeating is not fast enough, the human sight would feel twinkling.
Ferry Porter Rule and Critical Fusion Frequency
So, how high the frequency can eliminate the twinkling? Ferry-Porter rule points out, when watching a pulse illumination, coming with the improvement of the pulse repeating frequency, there is a critical point for human eyes. People will feel the illumination continuous, when the frequency is higher than the critical point. That’s we call Critical Fusion Frequency.
Refresh Rates for Full Color LED Screens and LED Displays
A refresh Rate defines how many times the content on the LED display repeats in each second. According to the Ferry-Porter rule, and our experience, to eliminate the image twinkling, the refresh rate for full color LED displays should be higher than 240Hz, and for full color LED displays with a brightness higher than 4000nits, the refresh rate must be higher than 400Hz.
Refresh Rates for Full Color LED Screens for Camera Recording
If there is a camera catching the image and video on the LED display, or when relaying a TV broadcast (LED screens for stages, arenas, events, etc.), it’s necessary to enhance the refresh rate to 2000Hz+. For LED displays and LED screens, it is enough to ensure the smooth image and video with the 50/60Hz Frame-Changing Frequency. And the meaning is not so big to improve further.
Disadvantage High Refresh Rates for LED Screens
As a disadvantage of high refresh rate, the LED display lifetime would be short, to a certain extent.
- LED Screen Power Consumption Explained
One of the most asked questions is how to calculate the maximal power consumption of a LED screen. Well first of all, you should know the input current and the voltage of the LEDs on the LED screen. Theoretically, in a labratory environment the greatest input current of the LEDs on a LED screen is 20mA, and the voltage for the LEDs for the LED screens is 5V. But in reality, the current of the LEDs of a LED screen can’t reach 20mA. So the power consumption of a LED is 20mA x 5V = 0.1W. So it is very simple how to calculate the power consumption of one LED on a LED display.
Pixel Configuration of LED Displays
And secondly, what you should know is the pixel configuration of the LED display and the resolution per square meter of the LED display. When you get this data you will know how many LEDs are available on the LED display. For example, let’s take a LED display with a pixel pitch of P16mm, the pixel configuration is 2R1G1B, which means that each pixel consists of 2 red LED’s, 1 green LED and 1 blue LED. So this means that every pixel has 4 LED’s. And the resolution per square meter of pitch 16mm LED display is 3906 pixels, which means there are totally 3906 pixels in one square meter. According to the previous data the calculation will be as folows: 4 x 3906 = 15,624 total LED’s per square meter for this LED display.
Maximal Power Consumption for LED displays
There are two types of driving methods for LED displays, which is the constant static driving method and the scan driving method. First let’s explain how to calculate the maximal power consumption and average power consumption of a pitch 16mm LED display using constant static current driving.
Constant Static Current Driving Method
The maximal power consumption of a pitch 16mm LED display is 15624 x 0.1W = 1.56Kw pero square meter. The average power consumption of a pitch 16mm LED display is 1.56Kw / 2 = 780W. This calculation way is for static constant current driving LED displays.
Scan Driving Method
For scan driving LED displays, you must notice that it has a 1/4 driving, 1/8 driving or 1/2 driving. Taking a pitch 6mm indoor LED display as an example, the usual driving method is 1/8, so if you calculate according to above way, the maximal power consumption of a pitch 6mm indoor LED display will be extremely high and gives us more than 8Kw per square meter. But in reality it is not correct, the reason is that you need to make the total calculation result divided by 8 because the driving method is 1 over 8 (1/8), and like that you get a maximal power consumption of 1.1Kw per square meter.
- The Relationship between LED Screen Brightness and Viewing Angle
What is the difference between a LED screens’ brightness and viewing angle. Well depending on the environment (indoor or outdoor) where a LED screen is installed, the requested brightness of a LED screens is different according to the environmental contrast ratio.
Difference between Indoor LED Screens and Outdoor LED Screens Brightness and Viewing Angle
Indoor LED screens request a lower brightness but request a high viewing angle. On the other hand outdoor LED screens’ request a higher brightness, and also a much better better grey grade. Therefore the outdoor LED screens’ viewing angle request is not as high as an indoor LED screen, generally between ± 35–± 50 degrees.
Relationship between LED Screens Brightness and Viewing Angle
If the viewing angle of the LED screen becomes lower, the LED screen brightness will be higher, or vice versa. If the contrast ratio between LED screens’ brightness and environmental brightness is higher, the led screens’ showing performance will be more colorful. However, if the brightness of the LED screen is too high, it is bad for the human eye, and much more power consumption will be wasted. Also much more heat will be produced, and then the temperature becomes much higher. For that the led chip’s brightness decreases much faster, and of course, its lifespan will become shorter.
Hereby, LED screens brightness and viewing angle should be applied to the LED screens’ environment.
- What LED brand to choose when buying a LED screen
The LED’s are surely the most important quality criteria when it comes to LED video displays. They determine the image quality of the display and are decisive in determining how the image quality is retained over time. The quality characteristics for LED’s are very diverse, and, here too, the maxim applies: the most expensive choice is not always the best choice. To highlight an example from the automobile industry: You are sure to be able to spontaneously list a variety of luxury sedans, though you may not generally consider these when selecting a new vehicle. Price and purpose play major roles in the decision of which model to choose. And also, luxury sedans differ in many ways, although they often all meet the highest quality standards.
The quality of an LED is determined primarily by the chip used. It determines the service life of the LED and how the lighting behavior of the LED changes over time. The mayor Chip manufacturers of LED’s are:
The prevailing opinion on the market today is that LED’s made by Nichia are the best for use in LED video displays. However, they are also undeniably the most expensive LED’s on the market by a wide margin. The price of LED’s varies on average from less than one cent per LED to up to 15 cents and more, depending on the type of LED (RGB LED’s with three chips in one housing are often more expensive). An extensive price difference can arise in manufacturing, depending on the LED’s used.
The most important factor for purchasing a LED screen and determining which LED’s to choose are:
Brightness: The brightness of the LED’s is measured in mcd (milli-candela). The higher the brightness, the better. You can run the display at a lower brightness, thus increasing the service life or increasing visibility during the day when the sun is shining.
Electrostatic Discharge(ESD): The LED chips produced by various manufacturers differentiate themselves through a varying sensitivity to the effects of electrostatic discharge (for example due to contact). Display failures caused by electrostatic discharges can be prevented by implementing safeguarding measures against ESD in the production process. The following LED chips listed are indicating the voltages that the LED’s can withstand in case of electrostatic discharges:
Taiwanese LED Chips: 800V
Chinese LED Chips: 200~800V
Sensitivity to Temperature Variations: Poor LED chips can fade faster, i.e. their service life can shorten, if they are exposed to high temperature variations. Depending on the country, temperatures can become extremely hot or cold during the summer or winter months, respectively. As a result, a poor LED quality could cause premature fading of the overall, expensive LED display.
General Service Life: The general service life of the LED’s often lies between 50,000 and 100,000 hours. (100,000 hours equates to 10 years of continuous display operation at full white, if no other factors exist which reduce the service life; such as increased heat in the display housing, or operating the LED’s at overvoltage in order to balance brightness reduction.
Brightness Reduction due Aging: Below is a table indicating the lighting reductions which arise within the first 10,000 hours: LED brightness reduction after the first 10,000 hours, sorted by manufacturer:
For the advertising screens we recommend always Silan LED’s, or the Cree LED’s which are a little more expensive than the Silan LED’s. Nichia LED’s, which are at least twice as expensive than Silan LED’s, for LED screens is mostly used for the professional industry like on stages or for television programs where quality is of high importance due to the high brightness and longer lifetime, and professionals invest a higher amount to have the screen performance and quality optimal at all times if not they are out of business and glamour is important in those industries. For advertising screens which are placed outside that quality is not necessary to be as optimal as the professional industry like stages or television programs because the screen is seen as an investment to shorten the ROI to less than 1 year and using the screen for advertising for over a period of at least 5 years to 8 years and gain 5 to 7 years from advertising.
If investing in Silan LED’s the initial investment is about 25%(Cree) to 50%(Nichia) lower than investing in Cree and Nichia LED’s. So for that Silan LED’s will have an ROI of around 1 year depending on the portfolio of clients that the screen owner has, the place where it is placed and price of the advertisements. When advertisers want to publish their products on the screen, of course quality is important but in practical terms the selling price of the commercial space on the screen will be the same if used Nichia or Silan or Cree LED’s because they don’t care about the lifetime and differences of brightness between Nichia, Silan or Cree LED’s, they just want to be seen and promote their products and or services on the screen. What is important for the publicity clients is the resolution, if it doesn’t look pixelated they do see that as a plus and will attract more advertisers because the better the resolution the higher the impact of the advertisement and the higher the company’s goodwill of the product announced. Also for Nichia and Cree LED’s the ROI is one and a half to twice the time in comparison to Silan LED’s which is two years at least.
Normally Silan and Cree LED’s need 100,000 hours to reach around 40% of its total original brightness, Nichia will need 100,000 hours to reach 60% of its total original brightness. This is because the materials used are much more expensive for the Nichia LED’s than for the Cree and Silan LED’s and are better conductors. Besides Nichia uses around 50% of the energy used to burn the LED’s in comparison to the Silan and Cree LED’s. For example 1sqm of 16mm pixel pitch Silan and Cree LED’s consumes around 1200W/m2 and Nichia 575w/m2 which is less than 50% to get the same amount of brightness.
Many of the quality factors for LED’s play a role in how they behave over time. Nichia LED’s are the only ones for which it is generally known that they thoroughly meet the required criteria, positively setting themselves apart from other LED’s on the market. The long-term values for some of the other manufacturers were not available. Many developments in the LED field are so new that long-term values over five, ten, or more years don’t exist yet. If price and performance should be balanced, we recommend LED’s with Silan chips. In terms of overall service life, Silan LED’s are 1/3 weaker than Nichia LED’s but they cost significantly less. With the service life of Silan LED’s, you can run your display for 6 years of continuous operation at full white, although running the screen at full white is never done in reality. In displaying average video image content, the effective service life increases by two to four times as much, that is, 14 to 28 years, depending on the image content. In contrast to the still very expensive Cree LED’s, Silan LED’s age more evenly and also don’t have as much lighting reduction after 10,000 hours. This proves particularly lucrative when exchanging individual pixel cards, since the calibration requirement is lower.
- Color Depth (Gray Scale) of LED Displays
The LED display color depth, or gray scale, indicates the process depth of the colors showed by a LED display. When looking at the technical specifications of a LED display given by LED display suppliers you can always find values like “12-bit, 14-bit, 16-bit”. Many clients and even sales executives don’t know what this value means. For that this article will explain what the color depth, or gray scale, means.
1-bit color (21 = 2 colors): often black and white
2-bit color (22 = 4 colors)
3-bit color (23 = 8 colors)
4-bit color (24 = 16 colors)
5-bit color (25 = 32 colors)
6-bit color (26 = 64 colors)
8-bit color (28 = 256 colors)
12-bit color (212 = 4096 colors)
14-bit color (214 = 16384 colors)
16-bit color (216 = 65536 colors)
So from above table, it’s not difficult to find the color depth actually shows how many colors can be shown on the LED display.
As well-known, LED display is RGB color model, and each pixel consists of red, green, and blue color LEDs. And here we will explain further about it in below table:
12-bit: there are 4 bits (16 possible levels) for each of the RG,B LEDs. So it would show totally 16x16x16=4096 kinds colors.
14-bit: In 14-bit process depth, there’s a little difference from 12-bit. For the reason that human eyes are not so sensitive to blue, than red or green. So it is assigned one bit less than the others. So for red and green, there are 32 possible levels, and for blue, there’s 16 possible levels. So totally it can show 32x32x16=16384 colors.
16-bit: It is very similar with above. But this time it’s due to the green color are most sensitive to human eyes. So it’s assigned one bit more than the others. So for red and blue, there’re 32 possible levels. And for green, there are 64 possible levels. So it can show totally 32x32x64=65536 colors.
Within the LED display industry many LED screen suppliers do not pay that much attention wen making the LED displays’ technical specifications accurate. And the technology homogenization is currently very serious. The true situation is, for the widely-adopted technology, the highest color depth is actually 14 bits. It is not arbitrarily speaking because it’s limited by the hardware part.
If adopting higher level IC and system, it wont be any problem to realize the 16-bit color depth or gray scales. But with nowadays tech, it must lose the virtual pixel technology. And actually the 14-bit color depth or gray scale doesnt make any big difference from 16-bit color depth for the human eye.