LED Walls Part 1 – Let’s discuss how they work and the details…

A LED wall is a bit of a different technology than projection. It is an emissive vs reflective method of displaying an image.

Projectors work by using light and an imaging panel that is typically 3/4-1″ diagonal and has somewhere between 1 million and 2.3 million pixels for today’s 16:9 or 16:10 projectors. (That is a whole lot of pixels in a tiny area!!). The projector shoots light onto a screen or wall and you then see the reflection of that image.

So back to the LED display. It is made up of multiple panels which are made up of smaller modules which then have multiple multi-color LED’s on them. A typical pane size is 500x500mm or 19.7×19.7″. Four of these panels makes up one square meter. The LED’s are directly emitting light out and generally are surrounded by a black plastic housing. This method offers a high visible contrast ratio vs. projecting onto a white screen and expecting it to be “black”. In a dark room projectors do quite well, but in high ambient light the LED wall can much more easily overcome the light and offer a brighter image.

A typical panel will have it sold and marketed by its pixel pitch. What this is a measure of is the distance between each LED on the panel. The current standard pixel pitches for what you would normally find in a church today is 6mm-3mm. Outdoor LED products like billboards and gas station signs are also in the same family but tend to have a much wider pixel pitch as the viewing distance is much greater and the eye has a hard time distinguishing the individual LED’s at a distance. When you are close up you need the tighter (lower numerically) spacing on the pixel pitch.

A key point here is that a significant part of the cost in a LED wall is what pixel pitch you choose. For example, a single panel of a 3.91mm pixel pitch would have a resolution of 128×128 pixels and over 16,000 LEDs on it. Can you imagine wiring up and making that all work? Yea… And that is 16,000 for each of Red Green and Blue…

A 5.2mm pixel pitch panel has a resolution of 96×96 and about 9000 LED’s

A 7.8mm pixel pitch has 64×64 pixels and about 4000 LEDs. This is only 25% of the 3.91mm yet the pixel count is 128×128 vs 64×64…

If you go up to let’s say a 2mm LED then your pixel count goes through the roof, and the cost follows.

So to make a 16:10 widescreen video wall that has the same ACTUAL resolution as let’s say a WUXGA (1920×1200) projector would at a 3.91mm pixel pitch require you to have 15 panels wide and 9.375 panels tall. Whoops, I can do that – it’s either going to be 9 or 10 panels tall. If we go 10 that would be 1280 pixels tall and 1920 wide.

Well, what if we just did 16 panels wide and 10 tall? That is 2048 pixels wide and 1280 tall. A true 16:10 aspect, but not a standard resolution.

So size — how big is 16 wide by 10 tall?

26.2′ wide by 16.’ Tall. That is huge.

So let’s say you do a 16′ by 10′ wall? 10 panels wide by 6 tall gets you close — 16.4′ by 9.85′. That is 1280 pixels by 768 pixels… Or really close to WXGA resolution which is 1280×800.

So the cost vs resolution on LED walls is something we will explore in a future post.

Please ask questions and I’ll continue to post more about them and photos in my upcoming blog posts.

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