The future looks bright for LED backlit screens. Adam Turner dissects LED, including the difference between old and new Bravias and Macbooks.
Sony is pushing RGB Dynamic LED backlighting in the 46in and 55in versions of its new Bravia XBR45 series. Meanwhile, Samsung's Series 9 LCD TV has "LED Smartlighting", which Samsung says results in vibrant colours and "arguably the most stunning picture ever seen on a television."
The key benefits are reduced power consumption and greater contrast - offering blacker blacks with more detail in the shadows.
LCD vs Plasma
LCD screens are generally brighter than plasma screens, while plasma offers greater contrast. LCD uses an electric field to manipulate tiny crystals, with a backlight shining through them to create various colours. Plasma uses an electric charge to turn gases into a plasma which then excites phosphors to emit light.
In other words, LCD starts with a bright screen and then tries to block the light, whereas plasma starts with a dark screen and then creates light.
LCD backlighting
There are several different backlight technologies available for LCD screens and the previous generation of Bravias and MacBooks used CCFL (Cold Cathode Fluorescent Lamps). CCFL backlights use several fluorescent tubes stretching behind the length of the display, where as LED employs a series of LED lights spread behind the display.
LED backlighting - blacker blacks, faster response
LED lights can dim further than CCFL lights, allowing for the creation of blacker blacks, and offer a faster response time. The switch to using an array of LED lights also makes it easier to dim sections of the blacklight, allowing the portrayal of dark shadows in one corner of the screen and bright sunlight in another.
White LEDs vs RGB Dynamic
While many LED backlights use white LEDs, Sony's new XBR Bravias use RGB Dynamic LED - employing a cluster of red, green and blue LEDs to create the backlight. This allows for more realistic colour reproduction than using white LED backlights.
The ability to dim the backlight and vary its colour reduces power consumption in comparison to CCFL. LED backlights are also thinner and lighter than CCFL backlights, assisting in the quest for wafer-thin displays.