You probably already know that LED technology makes these large screens possible. LED is a semi-conductor that emits visible light when electrons pass through it. From the exterior, it may look like a small lamp, but it functions in a totally different way. In fact, the emission of light depends on electrons flowing between anode and cathode within the LED chip, and the color of the visual emission depends on the materials utilized.

Putting many LEDs together forms several pixels. By definition, a pixel is the "luminous dot" present on every LED full-color giant screen. This luminous dot can be formed by one or more LEDs, depending on dimensions and features of the screen. On full-color screens, the pixel is formed by the three basic LED colors, which are red, green, and blue that, together, can form white.

The human eye has three types of receptors for daylight vision, and each one corresponds to a primary color. Any other color is the result of the simultaneous stimulation of these three types of receptors, after a phenomenon called addition synthesis that mixes the chromatic components captured by the eye. The mix of the three primary colors, in different percentages, allows the pixel to generate any possible color.

Each square meter of the LED screen can contain from 1,024 pixels (32*32 pixels) up to 9,216 pixels (96*96 pixels) depending on the models. The number of pixels can vary on the same surface because of pixel pitch. The pixel pitch of an LED display defines the distance between the pixels, expressed in millimetres. This is a defining factor of a giant screen's viewing distance, for the following reasons: the closer the pixels are, the closer the minimum distance but higher the screen cost per area; and the further apart the pixels are, the further away the minimum viewing distance is and the lower the screen cost per area. Therefore, the pitch determines the image definition and cost of the screen. Low pixel pitch equals higher definition and cost; high pixel pitch equals lower definition and cost.

You would determine what pixel pitch you need by defining the minimum viewing distance (MVD). The MVD is the closest you can get to the screen before the pixels start appearing as dots. Each LED giant screen manufacturer has its own method on how to calculate the MVD of a screen. There is not an absolute answer, because each one of us has a different eye's perception. A fairly precise and easy way to calculate the MVD would be converting the pixel pitch into distance. For example, a maxi-screen with 10mm pitch has a MVD of 10m, while a 20mm pitch screen has a MVD of 20m.

Why would I ever go for a higher pixel pitch and, therefore, a lower image quality? For two main reasons: one is financial, and the other is biological. The financial reason is pretty obvious: the higher the number of pixels on the LED screen, the higher the cost. It's important to note that, since the visible area of an LED screen has two dimensions, when reducing the pixel pitch, the LED density increases exponentially. In fact, reducing the pitch by the 50% increases the number of pixels by 400%, and cost follows. Let's take, for example, 1sq.m: with a 20mm pixel pitch, you have 2,500 pixels (1,000:20=50; 50*50=2,500 pixels), but with a 10mm pixel pitch, you have 10,000 pixels.

The biological reason is just as important: the human eye is not able to recognize small details from long distances. Therefore, from longer viewing distances, the human eyes won't notice the details that a high-definition LED screen can show. This brings us back to the financial reason. If you watch an LED giant screen from a huge distance, why use a high-definition screen when your eyes won't appreciate the superior performances?