DIGITAL DISPLAYS 26 www.stadiaworld.com LED-TECHNOLOGY: KEY FACTS AT A GLANCE •LEDs are diodes, in which electrons emit radiation energy in the form of light. •For multicolour image reproduction, units comprising three diodes (red, green, blue) are required to reproduce the whole colour spectrum in the RGB colour model. •Three of these diodes together constitute one pixel. •Pixel pitch defines the physical resolution of a system – the smaller the distance of the diodes from each other, the higher the resolution. •Virtual pixels are created when software simulates a fourth diode. •SMD technology groups three diodes on each printed circuit board, thus achieving higher resolution. •Resolution is related to viewing distance: the smaller the pixel pitch, the nearer the viewer can be to the LED module, and still see a good quality image. (With a pixel pitch of 20 millimetres, the minimum viewing distance is 20 metres.) •The colour depth (bits) denotes the number of possible brightness gradations per pixel. For example, 8 bits = 256 gradations per diode = 16.8 million gradations per pixel. •The processor power of an LED system influences the frequency at which it can generate the countless individual images, which the human brain interprets as moving images. The rendering frame rate is measured in hertz and megahertz (Hz/MHz). •The luminance of LED displays is generally given in the unit “nit”. For example, outdoor video walls typically measure 5,500 to 8,000 nits.
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