An LED screen is a video display, which uses light-emitting diodes to form images. An LED Module is a collection of light-emitting diodes on the surface of a moisture and airtight PC board. LED modules form the panel of a small display. An LED Cabinet is an enclosure comprising a panel, power packs, data cables and graphics receiving card. A matrix array of LED cabinets form the larger LED display or screen. LED screens are usually coupled/assembled per square meter. A basic matrix array, for instance, can be 3X4, which means 3meters height by 4 meters in length. A 3X4 LED screen has a surface area of 12m2.
Types of LED Screens
There are two types of LED panels: Dual In-line Package (DIP) and Surface Mounted Device (SMD) panels.
Older screens were built around DIP LEDs, also known as individually mounted LEDs. Clusters of red, green, and blue diodes are driven together to form full-color pixels, usually square in shape. These pixels arespaced evenly and measured from center to center for absolute pixel resolution.
More recent indoor screens are built using SMD technology—a trend which is now extending to the outdoor market. An SMD pixel consists of red, green, and blue diodes mounted on a chipset, which is then fitted on the driver PC board. The individual diodes are smaller than a pinhead and are set very close together.
DIP based displays have farther maximum viewing distance than the SMD based screens;however, the SMD screens proffer better image quality, higher refresh rate,and wider viewing angle.
Some important features to consider when choosing an LED screen are:
• The purpose and Installation Site
• Data update method
• The minimum and maximum viewing distance (Pixel Pitch)
• The distance from power source and control station
• The viewing angle
• The screen refresh rate and aspect ratio
• Protection rating
• Budget
The Purpose and Installation Site:
The purpose and installation siteof the screen is an important factor to consider because the various types of screens have certain advantages over each other. For instance, while the SMD proffers better resolution and contrast than the DIP, the DIP offers higher brightness and a farther maximum viewing distance. DIPs are better for outdoors where higher brightness but lower resolution is required, whereas SMDs are more adequate for indoor and outdoor installations where precision and image quality is paramount.
Data Update Method:
Thisconsiders how content can be uploaded or fed to the screen. Some screens are set up forlive video, while others show cycled videos and slideshows. There are two categories of the graphics card,which best suit the screen operator’s needs; these are Synchronous and Asynchronous Graphics Cards.
TheSynchronous Card works directly with a computer and mirrors whatever is on the desktop to one or more screens; it does not possess onboard memory and data can only be updated to the screen via high-speed LAN.It can, however, display contents from an external video source such as TV-cards, Video Cameras, DVD players etc.
The Asynchronous Card can work independently of a computer; it has a memory ranging from 2GB to 32GB, which can be updated via USB or via LAN. It cannot play live video content, only what isstored in its memory. Synchronous graphics card are suitable for all conditions and data update
The minimum and maximum viewing distance:
This refers to the distance between the screen mount and thenearest and furthest viewers of the screen respectively. With reference to a hall, the minimum viewingdistance refers to the front row seats, whereas the maximum viewing distance refers to the last rowseats. With reference to outdoors, the minimum viewing distance is the point of the nearest passer-by,while the maximum viewing distance refers to how far one can go and still adequately, view the image can. Unlike LCD television, LED screens aremadefrom clusters of diodes; the tendency for independentpixels being viewed instead of the intended image arises. The 'pixel pitch' is the main screen characteristic, which determines the maximum and minimum viewing distance of a screen.
Pixel Pitch is thedistance between diode clusters (pixels) as arranged on LED modules and it is graded in millimeters. Forinstance, a screen with a pixel pitch rating of 'P10' means the distance between pixels on the screen is 10mm while a screen rated P3 has a pixel pitch of 3mm. In practical terms, the pixel pitch translates tothe minimum viewing distance in meters. This implies that a screen with a pixel pitch of P10 has aminimum viewing distance of 10meters. The maximum viewing distance increases proportionally withthe pixel pitch and the size of the screen.
The distance from power source and control station
This is also of importance while choosing your screenand its peripherals. Certain ‘Synchronous’ graphics sender cards can only transmit via a data cable lengthno greater than 30m, some others 50m and even others 100m.
Visual data is transferred from computer to the screen at a minimum speed of 1Gigabyte per secondhence Wi-Fi devices cannot function with them considering available technology. Also, the screen mustbe fixed at a point with an adequate power source in terms of loading capacity and cable management. Forremote and off-computer operations and screen updates, ‘Asynchronous’ graphics cards may be required.
Viewing Angle
Although less troublesome in P3 and above rated screens, this can be an issue to considerin shorter but wider halls. The SMD has a better viewing angle than the DIP, however, the pixelation onDIP modules makes up for viewing angle inadequacies.
The screen refresh rate and aspect ratio
Also depends on the purpose of use and other visual equipmenton the media network. The screen refresh rate should be at par with video cameras, satellite TV signalsand live feed equipment otherwise image flickering and unsynchronized video-sound outputmay occur.
Video playbacks are better viewed on wider screens than on higher, whereas still images and slideshows are dependent on the crop and nature of the images. A good graphics control card and video processor should proffer flexibility in handling refresh rate and aspect ratio settings.
Protection Rating
This is the screen’s ability to withstand moisture and dust. Most screens are rateddifferentlyfor front and back. The international standard rating for electronics is the "Ingress Protection" (IP) rating.
An example IP rating is ‘IP65’; the first number refers to dust resistance whereas the second represents water resistance. So a screen with a protection rating of IP65 is totally impervious to dust and can resist water poured directly on it. An IP rating of ‘67’ means the screen is impervious to dust and can besubmerged in water 1m deep.
Most indoor screens have ratings of IP20 and IP33. These screens are considered well protected in temperate regions; however, for tropical regions like sub-Saharan Africa, we recommend a minimum of IP43 protection rating. It is necessary for outdoor screens to have a protection rating of IP65.
Budget
This may be one of the most important things to consider because there are too many specs andaesthetic designs of screens in the market. A P6 screen is more expensive than a P10 for instance. Henceif a client desires a screen with better minimum viewing distance than a P16 but cannot afford a P6 or P8, he can opt for the cheaper P10 or P12 which gives better picture quality than the P16. There are also flexible, customizable shapes and see through screens in the market, which may fit aesthetically with the client's décor, but the budget is best considered in such situations.
