LED display systems are popping up everywhere—from supermarkets to high schools, department stores, casinos, and sports venues, to just about every public venue imaginable. All for good reason—the picture quality and economics of LED displays have never been better. They provide one of the most efficient and proven means of engaging people’s attention of all demographics. LED displays have also proven to help create new revenue streams by enabling users to easily display sponsored content. It’s a win-win solution, where LED displays can deliver more than enough ROI to pay for themselves in a relatively short time.
Even though there’s been great traction for LED displays use in various applications and venues, it’s still a relatively new medium for many imaging professionals. There are numerous factors to evaluate to ensure you provide and/or get the LED display system that meets your needs and viewing expectations. This is the first in a series of columns to be featured in Wide-Format Imaging that will explore various aspects of LED display system technology, and the core parameters surrounding selection and implementation of best in breed technologies. So naturally, let’s start at the beginning of the selection process.
LED display systems are very different from standard flat screen HD displays. They are available in many different resolutions for different applications, can be virtually any physical size and shape, and are often viewed in direct sunlight outdoors from varying distances. So there are a number of criteria to initially consider to guide the selection and evaluation process that can dramatically impact the effectiveness of your LED display system. Let’s take a look at a simple four-point checklist to get things started…
Where do you want to position your LED display to ensure the best viewing angle? Typical LED displays feature 140 degree viewing angles, so you want to keep your audience as centered as possible to the LED display. Proper positioning of the display is critical to achieve the optimum impact on the viewer. The general rule of thumb is to position displays so that the maximum number of potential viewers are within a 120 degree viewing angle. This will help ensure the LED display receives high exposure with the majority of your potential audience.
What type of content do you intend on displaying? Not all content requires HD resolution, but chances are you will want to reserve that option for special events or future needs. In any case, the type of content to be played will determine the resolution (total number of pixels) you need. For example, when running text and graphics such as brand or school logos, with viewers no closer than 15 to 20 feet from a display that measures 4x8 feet, you can achieve acceptable quality with approximately 20,000 pixels. A 16mm pitch LED display at this size will yield only 12,800 pixels and create a grainy pixelated image quality; whereas a 12mm 4x8-foot LED display will produce a 112x208 matrix of 23,296 pixels producing more attractive and readable text and graphics.
The general rule of thumb for still photos and video is to deploy a minimum of 50,000 pixels to create acceptable images. Using 4x8 feet as our estimated display size, you would need the minimum of 8mm LED pitch in a 160x320 matrix to produce 51,200 total pixels. This display configuration will yield good results at a reasonable estimated minimum viewing distance.
For example, Trans-Lux offers LED pitches that now range from as small as 1.5mm to produce plasma display like HD images even up close, to 24mm pitch displays for use in stadiums or for highway billboards. It’s important to note that the cost of LED displays gets higher as the pitch gets smaller to compensate for the higher density of LED’s. So it’s most important to determine where you want to install your LED display, and what type of content you plan to play so that you can accurately specify and configure the system that best meets your needs—and image quality expectations.
How do I determine what content composition will look the best in stills and/or video? You always need to consider how many total pixels you have to work with. For example, you simply can’t display a recognizable close-up of a person’s face if you only have 2,500 pixels in your display. Consider that reproducing the eye by itself, which takes up 10 percent of the close up image, you’ll only have approximately 250 pixels to create the pupil, iris, white, eyelashes, eyelids and eyebrow. Remember that on an LED display, each pixel produces a single color so shaded areas require even more pixels to reproduce accurately. If you plan on showing people/models up close, you’ll need to increase the density of the LED pitch in your display or you will not be pleased with the results. It’s important to remember that smaller LED pitch means greater resolution, and that you always need to be selective with content based on the confines of your total pixel count.
How much power do I need to supply to an LED display? The general guideline for estimating a display’s maximum power requirement is to allocate approximately one-half (½) watt per pixel. If you have standard 20A 110V service available, you can deliver approximately 2,200 watts of power. This will limit your display to a maximum of 4,400 (2,200/.5) pixels, which, in a typical 4:3 ratio display, equals a 56x72 matrix of 4,032 pixels. This is not sufficient for anything but a small display with limited text and graphics capabilities. The 4x8-foot 8mm LED display referenced above with 51,200 total pixels would require a total of 25,600 watts.
In most cases, you will need to supply additional power to ensure proper operation by sufficiently powering your LED display. Power requirements should be included in the initial discussions with your LED supplier/reseller.