Computer monitors with LED backlighting – is it all hype?
As this year draws to a close it seems a good time to reflect upon the progression of computer monitor technology. One of the major and defining monitor technology trends of 2010 has got to be the push of affordable LED backlighting. Although this technology surfaced earlier than this year it never really gathered much pace – until now. With many manufacturers such as Samsung, BenQ and ViewSonic focussing their current efforts almost exclusively on promoting this ‘green’ form of backlighting it is easy to get lost in the forest of hype. Like most things to do with monitor technology and indeed technology more broadly the marketing machine often puts an awful lot of spin on emerging technologies such as LED backlighting. With huge and misleading ‘contrast’ claims and the tendency to forgo the word ‘backlighting’ entirely – as if this is some technology distinct from ‘LCD’ monitors – we can appreciate the confusion this creates.
TFT Central, a truly excellent ‘computer monitors’ resource, has recently published an article on LED backlighting. Aiming to dispell some of the misconceptions and confusion that shrouds the technology, the article looks at the real advantages, the potential drawbacks and the different ways in which the technology can be implemented.
Key points from the article:
- LED backlighting has seen significant market growth recently and is now included in various panel types; IPS, VA and TN.
- An ‘edge backlight’ arrangement using white LEDs (W-LED) is by far the most common, especially on consumer models. Unlike more expensive solutions seen in some high end TVs and ‘professional’ monitors this solution does not offer independent brightness control for different areas of the screen. Uniform brightness is controlled by a ‘diffuser’ – but like most things this isn’t perfect and the use of LED backlighting does not magically eliminate the possibility of excess backlight bleedthrough.
- A ‘direct lit’ flat-backlight arrangement of white LEDs (W-LED) can be found on some high-end LED-backlit TVs but is not currently employed on consumer monitors. The LEDs are distributed evenly behind the LCD matrix and can be independently controlled to offer some degree of differential lighting of the screen.
- The third and most expensive type of backlight, generally reserved for some ‘professional’ monitors and high-end TVs involves using RGB (red green and blue) triads of LEDs in a similar arrangement to a ‘direct lit’ array. The direct use of coloured lighting extends the colour gamut of the monitor but is far more expensive and can lead to colour balance issues as LEDs of various colours reach the ends of their lives at different times.
- W-LED backlights are restricted to ‘standard gamut’, often 68% NTSC. This is slightly more restrictive than the 72% NTSC colour gamut typical of ‘standard gamut’ CCFL bulbs and certainly more restrictive than the >114% NTSC coverage of RGB LED backlights.
- LEDs can be rapidly controlled to give very high ‘dynamic contrast’ figures. The use of LEDs in a backlight do nothing to aid the important static contrast of a PC monitor.
- LED backlights, edge-lit in particular, can be very thin and create monitors that are thin and light. Some consumers find this an attractive and somewhat fascinating aspect of the technology.
- Unlike CCFL bulbs, LEDs do not contain mercury and can be recycled more easily.
- Perhaps the main benefit of the use of LED backlighting in computer monitors is the improved energy efficiency. An W-LED edge-lit monitor can offer a power saving of 30-40% over an equivilent CCFL backlit monitor at the same brightness. They also produce less heat as a result.