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What is an “LED”?

Light emitting diodes (LED) are special diodes that emit light when illuminated by the movement of electrons in the semi-conductor chips.

What is a “Pixel”?

LED pixels

A pixel (short for picture element) is an image component of an LED display’s overall resolution. The more pixels used to represent an image, the higher the resolution is to offer greater picture quality. In an LED display, a pixel can consist of 1 or more LED diodes. A monochrome or grayscale LED display pixel has 1 or more LED diodes of the same color. A color LED display pixel either has LED diodes of different colors or 1 single diode which contains semi-conductor chips that emits lights with different colors.

What is “Pitch”?

Resolution detail

12, 16, 20 mm comparison jpg

Pitch is the distance from the center of a pixel to the center of an adjacent pixel. Pitch is very important because for the same display area, the pitch determines the resolution of the display. For smaller, tighter pitches, you have more pixels per unit area thus a better resolution. Selecting the right pitch when you are purchasing an LED display may save you money as well as getting you the appropriate resolution for your particular application. Please feel free to contact us to help you select the right pitch for your display!

Matrix Resolution

An LED display’s matrix resolution represents how many pixels there is on the display. A display with a matrix resolution of 320 (h) by 480 (w) means it has 480 pixels from side to side and 320 from top to bottom. The higher the matrix resolution is, the better an image is represented on the display. As we discussed earlier, for a fixed display area, selecting a smaller pitch will increase the matrix resolution of the display which means better image quality.

RGB Display

Red, green and blue (RGB) are the 3 basic colors human eyes can perceive. By using an appropriate combination of red, green and blue intensities, many colors can be represented. An RGB display simply means it’s a full color display. However, how many colors can be shown on an RGB display depends on many factors. Two of the most important factors are the input data signal quality and the display’s color processing ability. For example, if the input video signal only has 8-bit of information per color, no matter how many colors your display controller can process, the display will only show 8 bits of shadings per color. AD SYSTEMS’ current full color display controller can process up to 16 bits of information per color, that’s total of 281 trillion gamma corrected color levels. However, most of today’s video input signals are less than 10 bits per color. Therefore the actual color depth showing on an AD SYSTEMS LED display is only as good as the quality of the input signal.

Degradation

Generally speaking, an LED diode will quickly lose about 20% of its initial brightness after the first 2000 hours of use. After that, the LED diode’s brightness only degrades at a very slow and unnoticeable rate, until it dies at the generally estimated lifetime of 100k hours. This unique degradation curve is the result of the nature of semi-conductor chips. When shopping for an LED display, it is important to keep in mind that the manufacturer’s claimed display brightness will drop about 20% after 2 to 3 months of operation. The brightness level after initial degradation occurs needs to be high enough for the application. Some LED  companies signs sold as outdoor models are modified indoor units that are not bright enough to be seen in the afternoon sun.

NIT- Unit of Brightness

NIT is the brightness measurement unit the industry usually uses to calculate the brightness of an LED display. It is calculated as the following:
NIT = cd per pixel X pixels per M2
Generally speaking, the average sun light brightness in North America is about 5000 NITs. It does not take an Einstein to figure that in order to have a readable display during the day, an outdoor LED display needs to be at least 5000 NITs bright after the initial 20% brightness degradation. Therefore, when you are purchasing your LED display, it is important to compare the brightness of displays from different manufacturers under sunlight to make sure you are getting your money’s worth and that your customers will be able to notice your display when driving by.

LED Diode Density

LED diode density is a good indicator for comparing LED display performance, given the displays are using similar spec or brand LEDs. Just like your car’s engine where more cylinders generally equates to more power. More LED diodes per unit area generally means higher brightness thus better performance. Density is an expression of the number of pixels per m^2 multiplied by the number of LEDs in each pixel. AD SYSTEMS’ mission has always been helping its customers to increase their business and increase community awareness. Because of this, AD SYSTEMS has always sacrificed its profit margin in order to use more LED diodes than our competitors from only the best LED manufacturers in the world, such as the #1 rated NICHIA LED, to ensure our customers have the brightest attention grabbing advertising medium outside their business location.

True Pixel Technology vs Virtual Pixel Technology

Pixel Comparison

Some LED display manufacturers use “virtual pixel” technology. They claim that “virtual pixel” doubles the actual resolution of screen, i.e., a screen with a physical (true) resolution of 320×240 pixels in reality is expressed as the “virtual” resolution of 640×480.   In a “Virtual Pixel” Display in an attempt to smooth out digital image, each pixel of the image corresponds not to an actual module pixel but to a light/data source, that is part of the group of pixels that form the “Virtual pixel”. By this mode of pixel sharing one pixel contains the “Virtual group”* of pixels image information. *(The 2 or 4 pixels that are combined to form the “Virtual” effect). Virtual pixels are also known as “pixel sharing” or “dynamic pixels”.  Some claim that with “virtual pixels” the displayed image has twice the resolution as the “physical” resolution. This is not true, since one module pixel cannot memorize or hold and display the majority of information from the initial pixel. The majority of the original information vanishes. This results in distortion of important details and other elements such as colors that are part of the initial image.

It is important to realize which method of pixel technology you are being quoted because sign companies often try to pass off virtual pixel displays as higher resolution displays. For example a 10mm virtual sign has a similar number of LED diodes to a 20mm true pixel sign. Most pitches that end in .5 are in fact virtual displays. The main reason virtual pixel technology is popular with manufacturers is they use 3 times fewer LEDs diodes to save money. Unfortunately this savings is rarely passed on to the customer and the performance or lack thereof of these signs leaves something to be desired. Side by side the difference in image quality is immediately apparent. The number of LEDs in a display is the single largest determinant to the cost of an LED sign. When shopping for an LED sign make sure you are doing an “apples-to-apples” comparison.

In the actual, physical or true pixel technology, the image displayed on the sign is an accurate, true-to-source reproduction as each pixel of the original image corresponds to an actual pixel on the screen.  It takes the actual color in a pixel as it is balanced in brightness and contrast and no additional corrections are required.

LED Diode Binning

The brightness rating of an LED diode is usually expressed in a range instead of a certain NIT value. This is because the core of LEDs diodes are made from semi-conductor chips thus even the best LED manufacturers in the world cannot control and guarantee that diodes manufactured within the same batch have exactly the same brightness. Therefore, LED manufacturers separate their diodes into bins of similar brightness. When a LED display manufacturer makes an LED display, it is important to use LED diodes from the same bin in order to maintain brightness and color uniformity. AD SYSTEMS uses only the top quality/brightness bin LED diodes from top LED manufacturers ensuring the LED uniformity of an AD SYSTEMS display is always among the highest in the world. We know when a customer installs an LED display at their business, it becomes part of their business image and we only want the absolute best for our customers!