LEDwalls Virtual Pixel

by : Fabio Aversa

So why do LEDwall use the Virtual Pixel Technology? And what is it exactly? These are very common questions when you approach the LEDwall industry for the first time. The answer might look obscure at first, but it is actually very simple once you understand a few basic principles. The Virtual Pixel is a video-management feature that allows a 400% increase in image quality. Yes, 400%. So why LEDwall manufacturers use it is pretty obvious: they use it to show better quality, realistic-looking images.

But why do LEDwalls need to increase the image quality through a video-management feature in first place? It's pretty simple: despite of its huge size, a LED screen has usually many LESS pixel than a common PC screen you are watching right now. How is that possible? Because on a LED screen, the distance between 2 pixels can be up to 30mm or even more. As a result, on a normal PC screen, you can have 1024 x 768 physical pixels or more - while on a 4x3 meters LED giant screen you could have 192 x 144 physical pixels! Big difference, uh?

So how can we actually see anything on a LED screen with a resolution of only 192 x 144 (27.648 physical pixels in total)? Easy! Thanks to the virtual pixel technology, we can double the number of pixels in length and the number of pixels in height: therefore we can increase the number of pixels perceived by the human eye, by 4 times! Therefore, the same screen with virtual pixel technology will have a perceived resolution of 384 x 288 pixels (or 110.592 pixels!). Isn't that beautiful?

Now you are probably asking how is that possible? Well, there are two different types of virtual pixel: the so called, "geometrical or squared" and the "interpolated". Let's start from the first one. geometrical / squared virtual pixel: this technology is based on a pretty simple geometrical concepts. If you have two identical shapes placed next to each other, by taking half of each shape, you can create other two identical shapes. Clear, isn't it? Now, as I said, if you have two identical shapes placed next to each other, by taking half of each shape, you can create 2 more shapes. For example, if you have 2 identical pixels lying next to each other, by taking half of each pixel, you can create 2 more pixels... identical to the first two.

So, what happen when you combine the first 2 Real pixels, with the second 2 pixels that you created "virtually"? You just doubled the number of pixels (from 2 to 4)! Now imagine to double the number of pixels you have in length, and - with the same technique - double the number of pixels you have in height: well, you increased the number of pixels (and therefore the image quality) by 400%!

So this is how the "geometrical / squared virtual pixel". Pretty good, uh? Unfortunately Not. There are some limitations and side-effects of this technology, especially when compared with the "interpolated technology" which is the latest technology used on LEDwalls. The geometrical / squared virtual pixel seems to be a pretty useful and "smart" technique. It uses half of two adjacent pixels to create other two. It is pretty easy and straightforward once you understand the mechanism. So what are the limitations of this technique? Well, there is only one main limitation, but it could be important. Let's see if I can explain it clearly:

We just saw how two adjacent pixels can create other two by "switching" the side LEDs of each pixel. In this case everything worked fine because the distance between the LEDs is the same distance we have between the pixels. But let's say for example that I have a LEDwall with a bigger pixel pitch, for higher viewing distances. What happen if the distance between LEDs and Pixels is not the same anymore? Well, in this case the virtual pixel you created is not identical to the Real Pixel anymore. The virtual pixels are more stretched then the Real ones and therefore the overall image quality will be affected.

Over the past 15 years some manufacturers developed a technology that allows to go beyond these limitations and guarantee a superior image quality with ANY resolution. Does it mean that the geometrical / squared virtual pixel is not a good technology? Well, let's just say that it is definitely not the most recent one! Some LEDwall manufacturers still use it, so be careful: when considering your LEDwall supplier, make you check how their virtual pixel technology works.