LED Displays

What are LED Displays and how do they work?

LED displays, the most confusing combinations of words to ever be encountered by creative individuals next to “it’s missing something…”. This confusion often stems from the fact that so many different products use LED technology and are displays, while only some call themselves LED displays. Confusing, right? Some of the screens we mentioned in the last section used LED technology. Some lighting fixtures we’ll talk about in later posts use LED technology. So what is the difference between those and the LED displays we’re focusing on in this section?

Well, you’ve probably heard of a bunch of different terms used for these kinds of displays, such as LED displays, LED walls, LED panels, video walls, LED signage, and more. You’ve seen them in more places than you probably realize. The giant screens you see at concerts and festival stages are all LED displays. All the signage you see on the outside of buildings or on large billboards off the highway are LED displays. You may have seen oddly shaped or curved signage or screens inside of malls, retail spaces, or building lobbies, and these are often LED displays.

But again, what makes these LED displays different than a computer monitor that also uses LED technology?

The main difference lies in their basic construction.

Computer screens or TVs that use LED technology have tiny LEDs all next to each other in a grid that make up the image. They are packed in together so densely that in most use cases you can’t identify the individual LEDs. The LED displays we’re referring to in this section are built with large LEDs that have visible space between them measured in millimeteres, which is quite a lot when compared to the nanometers of space between LEDs on your computer screen. These larger LEDs are capable of a much higher brigthness than your computer monitor or TV screen, and the spaces between them may seem strange as first (because of what it looks like from up close), but make much more sense when we talk about their implementation.

Take a look at the images below and you’ll get a sense of the difference. The first is the LED wall, typically seen on the outside of buildings or at festival stages from a foot or 2 away (hard to tell from the picture). You noticed the individual LEDs and how its hard to make out the image?

Below is a Macbook from less than a foot away, and notice how you don’t see any individual pixels? You see the image clearly.

If you actually got close enough or used a magnifying glass, you’d be able to look at your computer screen and see all the individual LEDs and the space between them.

Implementation basics

Signal flow

Before going through the advantages, here’s a quick run down of how you work with LED displays. You’re probably used to taking your computer, and plugging a screen into the HDMI port, et voila. Working with LED displays, it isn’t much more complex, but there are a few extra steps in the chain. Your computer generating content or playing back video will get connected to an LED processor/LED controller. This is a small rack unit that takes your regular computer output, crops it as needed for the size of the screen then translates the signal and tells all the LEDs on all the tiles what to do. So you don’t need to worry about doing anything too special. Depending on the resolution of your display and the amount of non-traditional elements you design, you may need to become comfortable with pixel maps (check the design basics section following).

One annoying thing is that all LED display vendors have their own proprietary LED processor/controller. So you generally always buy the whole package together from one vendor. These processors are often a prohibitive cost when working with small displays because the processor/controller can cost anywhere from a few thousand to tens of thousands of dollars, which if you’re only working with a small surface area, may put you out of budget. For larger displays, the cost becomes much more manageable as you’re able to cover much larger surface areas with these kind of bright and rugged LED displays than you would with traditional screens or projectors.

Advantages?

So what are the advantages to using and LED display? Well there are a number, but why use them if they image looks so pixelated? This is where implementation kicks in. We’ll talk about it as we go through the different advantages, but LED displays are generally used when the viewer is going to be somewhat distant from the screen itself. The farther you get away from the LED display, you stop noticing the spaces in-between the LEDs, and the image begins to look unified. Because we sit so close to our computers, we need the pixels to be very small and dense. The distance at which you stop noticing the spaces between the LEDs depends on the density of the LEDs, which we’ll address shortly, but it’s usually more than a few feet. But firstly, advantages:

Brightness

Bigger LEDs can be brighter, which make these displays bright and beautiful even outside on sunny days. New Retina Macbooks are around 350 nits in brightness, while LED walls can go from 700 nits, to 1500 nits and beyond. That’s more than 2x times as bright as your Macbook on its brightest settings. You can see LED displays from very far away, as you’ve noticed at many concerts and festivals. In malls or building lobbies they’re excellent, as even in bright settings they will pop with great colours, contrast, and visibility.

Weather resistance

LED displays are manufactured with higher IP codes than TVs and screens. IP codes are ratings that define how rugged something is against dust and water (the two destroyers of electronics). Many manufacturers produce LED displays that can function outside in rain, snow, sleet, sun, or anything in-between. This allows us to use these LED displays for building architectural accents, festivals, outdoor signage, and more. They’re much easier to integrate in outdoor settings than projectors or screens.

Seamless displays

One of the most interesting elements of an LED display is that there is a separation between the screen and the display controller. For TVs and computer screens, the display controller is locked inside the hardware and is setup to only be able to handle a few resolutions because the number of pixels in the screen are never changing. LED displays are a bit different because instead of buying a “screen” with a set resolution, you buy squares or half-squares with a bunch of LEDs on them in a grid. You can then take these pieces and make whatever “screen” you like from them. Unlike the screens in the previous post in this series, these individual pieces of the screen (often called tiles) do not have a bezel. So you can make seamless screens of any size and shape. You can make long screens, tall screens, pillars, square screens, triangle screens, curved screens, screens that wrap around objects, or broken-up-looking screens, or anything! We’ll talk more about this in the design section, but the important thing to note about the implementation is that you can fill almost any size space with a seamless screen. Below is an example of a single tile:

Lifetime and service

LED technology has been great for a lot of different sectors. Even inside your home, you have probably switched many of your lights to LED bulbs. This is probably because of the lifetime of an LED. Unlike traditional bulbs we used in our homes, which are similar to bulbs in projectors (albeit the new LED technology is making its way into projectors now as well), LEDs don’t burn out after a few thousand hours. They can often live for tens of thousands of hours. In your home, maybe this service call isn’t much of a hinderance, but when you’re talking about long-term/permanent installations in all parts of the world, having to buy new parts and make a maintenance call costs money. If you have to do this regularly, it can eat up a lot of resources. LED tiles that make up LED displays have very long lifetimes, ranging from tens of thousands of hours to 100,000+ hours. Because they come in tiles, if a single tile needs servicing, you don’t have to replace or repair the whole screen. Tiles come with the ability to be front serviced or rear serviced depending on the installation requirements, and over the long run, are quite affordable to maintain.

Design basics

Pixel maps/rasters

Pixel maps are simple. They’re guide images provided to you by the LED vendors or installation team that will tell you how to create content for the screen. LED displays can have a very large range of resolutions and can be non-traditional in shape and size. To make it easier for content teams creating custom content, processors will often take a 1920×1080 signal (the default most computers output these days), and then crop out and assign certain sections of that image to certain parts of the LED wall. For instance, if you had a screen that was 2 feet tall and 30 feet long, you would be given something like this:

The version you’d get from your vendor would be much nicer than this, but this would essentially show you where how to create content for your display, with pixel co-ordinates written in. In this case, because the screen is a single long display, to make it easier to fit on a standard computer/media player output of 1920×1080, the physical display is broken up into 3 quadrants, where the arrows mark edges that would be touching in real-life. You could then make your really long graphics in Photoshop of After Effects, then you’d crop and transform it to fit the pixel map given to you so that when you send the content from your computer, they would be mapped properly to the display.

Brightness scheduling

You should almost always consider programming the brightness of the LEDs based on the time of day. You may want them running at 80% brightness during the day when they’re competing with the Sun, but you’ll probably want to tone them down at night otherwise they will be painful to look at. Often times this can be done directly in the LED controller.

Viewing distance/Pixel density

This is a difficult element to design for and where many displays fall short or are unnecessarily out of budget. LED displays/tiles come with millimetre resolutions instead of pixel resolutions you might be used to. For example, you can buy LED tiles in 2mm, 4mm, 6mm, 8mm, 12mm, 20mm, 100mm, etc. The millimetre measurements refer to the spaces between the pixels we mentioned earlier. In a 2mm tile, the distance between the centre of two LEDs will be 2mm. In a 100mm tile, the LEDs will be 100mm away from each other. The correct term for this is pixel pitch. When we talk about displays being very dense, we’re talking about screens with a very small pixel pitch. The smaller the pixel pitch, the more pixels there are crammed together, and the higher the pixels per inch (PPI) are. PPI is simply a measure of how many pixels fit inside a 1 inch square. You may or may not use PPI when designing with LED displays since more often than not the number will be quite low (and therefore not very useful), but that is how most computer screens and high resolution monitors are measured currently. You’ll see specifications for laptop screens mentioning 300 PPI, or similar, which means every square inch of screen space has 300 individual pixels. Current standards consider 2-3mm to be very high resolution LED displays, 4-6mm being high resolution, 12-20 being a moderate resolution, and anything above that to be for long distance viewing.

Withholding any special usages that you’d like to achieve with LED displays, in a standard display situation with traditional content, some LED vendors say that you should calculate your viewing distance roughly by taking the millimetre pixel pitch and using that value as the number of meters the viewer should be away from the display. For a 2mm pixel pitch display, your viewer should be 2 meters away. Other vendors have different preferences and recommend multiplying your pixel pitch by 8 and using that as a foot measurement for your viewer. In the similar 2mm pixel pitch display example, your viewer should be 16 feet away, which is more than 2x the other vendor’s meter recommendations. As with any art, this viewing distance is purely an aesthetic preference, and the only real way to find your preferences are to Google some local LED vendors or rental shops and ask to come demo some of their units. You can test different resolutions from different distances and really get a sense of what might work for your project and what might not work.

Different setups and non-traditional displays

Ok, so, all the text so far was really only so that this area would make sense. The most interesting aspect of LED displays is their modularity allows you to be extremely creative with them. We mentioned some unique displays you could create, such as pillars, strips, broken-up pieces, etc. Let’s take a look at some projects we’ve been fortunate enough to be a part of, because pictures are worth 1000 words (and writing 1000 words takes forever…):

As you can see, these images summarize the elements we’ve been talking about so far. Different settings, indoors vs outdoors, bright even in the day time, high viewing distances, etc. These examples add non-traditional features, such as circular displays, LED sticks/strips, archways, multiple pixel pitch surfaces (high pixel density tiles mixed with low density tiles).

One of the interesting examples above is the Seattle Art Museum architectural piece with the LED tubes. Many LED vendors have “creative” LED solutions. Sometimes these are little bulbs, sticks, tubes, nodes, flexible curtains, transparent tiles, LED spheres, and more. They’re worth asking your vendors about because they end up being in-house solutions that differ from vendor to vendor.

Light source vs canvas

Because LED displays are so bright, designers often overlook the fact that LED displays can act as lighting sources while simultaneously acting as canvases for content. In the 221 Main image above, you can really see an example of the screens lighting the area a blue/white because of the water content. Think about this and try to take advantage of it. Sometimes you may or may not even need very complex content as you can fill a space with interesting light patterns using bright LED displays.

Wrap up and what’s next

LED displays are awesome. Use them creatively and you can create extremely unique installations. They’re rugged, bright, and can take on many shapes and forms. With LED displays under control, traditional screens under control, the next section will focus on the magic of projectors!