Conventional LCD TVs use backlights which are effectively thin fluorescent tubes behind the LCD panel. These can be dimmed, but are essentially always on, as the LCD panel produces no light itself - unlike a plasma panel - but merely modifies the light passing through it.
LED-illuminated TVs use LED lighting for the LCD panel. This can be a matrix of LED light sources behind the panel, LED sources at the edges of the panel, combined with reflective material to spread the light behind the TV, or what are called 'local dimming' LED arrays, in which many more LEDs are used. In the first two kinds of LED-illuminated LCD TVs, the lighting functions much as the tubes do in conventional TVs. In the local dimming models, the LEDs can be controlled in tandem with the LCD panel, so that for example dark areas of an image get much less - or even no - illumination, at the same time as bright areas are getting much higher levels. This can give better contrast and colour definition, but the effect depends on how small the clusters of LEDs are, and thus how localised the dimming can be. Some companies are using the term LED TV to set LED-illuminated LCDs apart from the kind using the longer-established tube lighting. It's called marketing.
and perfectly answering the question I was about to ask! Thanks! Is therefore, the "auto dimming" feature on my TV related to this contrast control?
See me ride out of the sunset, On your colour TV screen
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Cyrus CD6SE / Super High Breed / Kandy K2 / SHB / Spendor S6e / Grado SR80 / Sony TC-KE400S
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