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MillimeterAn Illuminating Technology
Jun 1, 2004 12:00 PM, By Jeff Sauer
LEDs bring new life to LCD monitors.
LCD desktop monitors have a definite allure among common business offices. Functionally, they save space on the desk, and emotionally, they just look cool. And, for most users, the quality of today's LCDs is excellent, with good brightness and contrast and nice sharp pictures. Detail-oriented content-creators, however, aren't adopting LCD monitors as quickly, and the reasons are straightforward.
LCDs still can't match the color depth of traditional CRTs. Video professionals are also sensitive to the slower refresh rates that have historically caused ghosting, although today's premium monitors are getting close to “good enough,” with refresh rates often less than 20ms. Still, a good old CRT does a better job.
NEC/Mitsubishi, in partnership with Lumileds, has developed an LED-backlit LCD monitor with greater color depth and faster refresh rates.
That's not to say that newer video production-oriented monitors, like Sony's LUMA series, don't have a significant role to play in video studios. For all the reasons thin LCDs make sense elsewhere — space savings, lower power consumption, high brightness, less reflection of ambient light — those monitors certainly have a place in production environments. LCD monitors are excellent for the tight quarters of broadcast switching and production rooms. And, saving space in production trucks needs no explanation.
Because of Sony's video production expertise, the LUMA series also addresses some of the specific needs of production environments. For example, Sony has removed the connectivity module from the monitor, linking it by a single cable of up to 10m and affording excellent flexibility in monitor placement. An added anti-glare coating can minimize reflection for production lighting. And, high-quality de-interlacing and scaling give the display the best visual information to work with. Yet, ultimately Sony has not made any dramatic changes to the state of LCD technology. While LUMA series monitors can be excellent solutions for seeing video feeds for switching, framing images, and selecting takes, even Sony would agree that LUMA monitors don't necessarily target the critical eyes of the color proofing experts or video editors making critical decisions.
However, LCD may yet get there. A new technology may bring top-caliber color accuracy. Lumileds is a company that manufacturers LEDs, and its Luxeon DCC LED technology is now being integrated into a prototype 21in. LCD monitor from NEC/Mitsubishi. That monitor uses two strips of red, green, and blue LEDs as LCD backlights in place of the traditional Cold Cathode Fluorescent Lamp (CCFL) backlights or sidelights of current panels.
What do LEDs offer that CCFLs can't? Basically, they are a digital, controllable, and programmable light source that can yield better color, better color depth and better color range, and even the possibility of fewer motion effects.
The combination of red, green, and blue LEDs grouped together in a light strip acts a little bit like the red, green, and blue light guns of old CRT projectors. By blending those primary colors to produce white, the LEDs can achieve a specific, even adjustable color temperature. That alone is a big advantage over traditional LCD light sources with one fixed color temperature.
More critical to rich, accurate color, and also like those CRT light guns, the mixture of red, green, and blue light can produce better saturated color (109% of Adobe RGB and 104% of NTSC color) than today's LCD monitors. Grayscales are theoretically much better, too. Compared to a fluorescent back- or sidelight that is always “on” with only duty cycle control of brightness, LEDs can control the light to display a broader range of grayscales without varying from a consistent color temperature.
LEDs also last much longer than fluorescent lamps, losing roughly 10% brightness over the same 50,000 hours over which fluorescent lamps might lose 50%. And, even as LEDs do lose brightness and change characteristics, the red, green, and blue strips can be reprogrammed to retain a consistent color temperature. Color temperature is also adjustable through the monitor's control panel to a setting that suits a specific application or environment best.
For LCD monitor manufacturers, LEDs can dramatically reduce the need to control light leakage. Because LEDs can be made to emit light in a specific direction, something like a collection of miniature flashlights, monitor makers can be less concerned with light emitting in the wrong direction. That focused light also makes evenly defusing light to cover the entire monitor easier.
Programmable LEDs can even help minimize motion artifacts in video on LCD monitors. Because LEDs are solid-state devices that can go on and off in as little as 20 nanoseconds, and because they are programmable, an LED light strip in video mode could be programmed to turn off as video moves from one frame to the next, much like a film projector. The result is less image ghosting. Taking things yet another step, future LCD video monitors could even buffer a handful of video frames, analyze brightness, and then display the most appropriate and efficient brightness on a frame-by-frame basis.
Of course, in terms of actual usable monitors, many of these advantages still reside in the domain of great potential, with no products yet available for purchase. Even NEC/Mitsubishi's as yet unnamed 21in. won't be available much before the end of the year. And while no price has been set for the product, it is certain to sell at a significant premium to the typical 21in. LCD monitor. “Significant premium” may over time and with increasing economies of scale come to approach mere “high-performance pricing,” yet LED-lit LCDs will likely remain more expensive to produce than fluorescent-lit LCDs for a while.
Still, it's a technology that shows significant potential for video content and one for which creative professionals, as well as high-end home-theater consumers, might well be willing to pay. Although NEC/Mitsubishi may turn out to be the only company to offer a product this year, that probably won't be true in 2005.
The dramatic success of LCD-TV products over the last couple of years is in spite of LCD technology's traditional shortcomings. Yet that success clearly suggests that there ought to be sizeable consumer market premium products with more vibrant colors in the same flat-panel sex appeal. Such brilliant color-capable monitors would make a distinct impression in the side-by-side selling environments of typical consumer electronics stores. Professional LCD video monitors may actually follow consumer products given the respective market sizes, but once the technology matures, it is likely to end up in professional products.
Indeed, LED-lit LCD monitors will probably remain premium products in both the LCD-TV and desktop monitor categories given the higher costs. But if it means seeing accurate color and losing ghosting artifacts, pros will probably be happy to pay a little extra, especially if in comes in a cool flat panel.
Jeff Sauer is a freelance video producer and industry consultant. He directs the DTV Group Lab, an independent research and testing facility in Cambridge, Mass.
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