LED Walls Part 5 – More information…

This post will summarize a few things that have already been touched on in other posts and adds new information to the mix.

First off – let’s discuss CALIBRATION further. This is a huge key factor in having a good looking LED wall. When the manufacturer orders their LED’s from the LED factory – the generally come within a 5nm window – say 570-575nm. This seems great, but if you really keep in mind that most humans can detect a color shift of 2.5-3.5nm, it’s something that can be noticed. So let’s say we get a LED wall with 3 million pixels? Do we just ignore the need for it to be tweaked, or do we do something about it?

The way you can “shift” the color or brightness in a calibration situation is to in the case of brightness, is to turn down the other LED’s that are shining at let’s say 1100 nits and if you have a section that is only putting out 1000 nits, you have to “turn down” the brighter LED’s to match the lower output ones. This will limit your maximum brightness output of the display to the weakest link of the group if you choose to calibrate to that level.

And for just a point of reference – in a batch of LED’s – it would not be uncommon to see a 10-20% variance in brightness when they are new, and as they age – they can shift to an even greater variance. One of the major contributors to the LED depreciation is heat, and the upper parts of a LED wall would likely be exposed to a higher heat load than those near the bottom. (heat rises, and the heat load from the entire wall will use the extrusion as heat sink area, with the top of the wall typically being the warmest.)

In most indoor church settings, you would be running the output much below the maximum so the total heat load would be greatly reduced, which would help extend the life of the components.

As for COLOR calibration – this was one that I had to bend my mind to think about, but similar to how the brightness calibration is done – the millions of LED’s in a large wall are not all going to be within 2.5-3.5nm of each other in color output, in one color, let alone three colors! Can you imagine trying to get over 16,000 pixels to be all the exact same RED, GREEN and BLUE output wavelengths? That is 49,152 LED’s in just one 19.7″ x 19.7″ panel of 3.91mm (or 128×128 pixels, as each pixel has red, green and blue)

So to just think – if all the LED’s were independent it would be one thing, but each pixel in the LED wall’s we are talking about combining the RGB LEDs into one unit. The order of magnitude is insane when you look at a large wall…

So to get all the GREEN LED’s to match up – most high-quality suppliers of a LED wall will get them within about 5nm. And if you work with color mixing – you can apply a slight amount of red or blue to shift the green color and get all the LED’s to be within a very close margin so they all look the same green. The same is done with the red and blue – by adding a microscopic amount of the other colors you can “pull” the color and then get a resultant color from each pixel that matches. The takeaway here? You are essentially shrinking the total color gamut in order to calibrate it if your LEDs are far off. The closer your LED’s are from the manufacturer the less you need to dial in the calibration and the better the overall picture and color gamut you will have.

The key point here is to make sure you get a product that has tight tolerances from the get go, and then realize that with age – several factors will need to be taken into consideration that will require you to re-calibrate it on a regular schedule. Just for a point of reference – how often does the piano or guitar get tuned? The LED wall – the individual LED’s can and do shift in output and color over time and in my opinion, a new LED wall should be calibrated and then again at about the 1-year point and on an ongoing schedule after that for the best-looking image.

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