An LED display consists of many closely-spaced LEDs. By varying the brightness of each LED, the diodes jointly form an image on the display.
To create a bright colour image, the principles of additive colour mixing are used, whereby new colours are created by mixing light in different colours. An LED display consists of red, green and blue LEDs mounted in a fixed pattern. These three colours combine to form a pixel. By adjusting the intensity of the diodes, billions of colours can be formed. When you look at the LED screen from a certain distance, the array of coloured pixels are seen as an image.
LED is a highly energy-efficient technology, hence the widespread use of energy-saving LED bulbs today. The amount of power the diodes in an LED display use depends on the type of display, brightness and usage.
There are many different types of LEDs and displays. The power consumption of an indoor display, for example, will be different from an outdoor digital sign, which has to be seen in direct sunlight. The brightness of the display is also a major factor. The images must be clear, but the light from the display must not dazzle. An outdoor LED display needs to be far brighter in daylight than when darkness falls.
What is displayed also has an impact. LED displays display images by turning on and adjusting the brightness of coloured diodes. An entirely white image with black text will therefore require many more illuminated diodes – and far more power – than white text on a black background.
It is difficult to say anything specific about the life of an LED display as many factors come into play. However, with proper maintenance, a display can certainly last for more than ten years. As with all types of electronics, life expectancy is also affected by the daily use and the environment around the display. Light images and a high level of brightness are more wearing on the display than darker images and a low level of brightness. Factors such as humidity and salt content in the air can also come into play.
Over the course of the life of an LED display, the light output from the diodes will diminish. By how much depends on the type and generation of the diodes. Many LED displays never use their full light intensity, so reduction will rarely be a problem.
The nit measurement is used when analysing the luminance of an LED display. Nit is another word for candela per square metre. Candela is the SI unit (metre system) of luminance. It is a unit that takes the human eye’s perception of the brightness of different colours into account. This makes it the obvious unit to use when measuring the brightness of a display. One candela is roughly the light emitted by a normal candle.
The nit unit is completely different to the ANSI lumens measurement, which is used to assess the brightness of a video projector. They cannot be compared.
The distance between an LED display’s diodes determines the resolution of the display. The distance to the centre of the neighbouring group is measured from the centre of each group of red, green and blue diodes. This distance is known as pixel pitch. Each group of diodes forms a pixel.
If an LED display has a pixel pitch of 1 cm, there may be 100 x 100 pixels per square metre of display. The resolution of a display is given as a pair of numbers that indicate the width and height in pixels. If you have a 6 x 8-metre screen with 1 cm in pixel pitch, it has a resolution of 600 x 800 pixels.
There are LED screens with a pixel pitch of anywhere from several centimetres to a single millimetre.
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