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LEDs in LCDs

Jan 1, 2006 12:00 PM, By Jeff Sauer

Does LED backlighting push LCD flatscreens closer to the color capabilities of CRT reference monitors?

Flat and thin LCD monitors have supplanted older, big-bellied CRTs and are now the default desktop display technology for newly sold computers. It's no secret why. They win on "cool" alone, but they also afford significant and practical savings on physical desk space. Less flicker is easier on the eyes, and high native resolutions produce nice, sharp computer text and graphics. Yet, as color professionals know, LCDs just can't match the color range of those old CRTs.

That, however, is not necessarily a limitation of LCD technology. A new technological approach to LCDs proves that flat panels can indeed achieve a wide color gamut. NEC's LCD2180WG-LED takes this new approach. The result is a color gamut that is 103 percent that of NTSC and 107 percent that of Adobe RGB.

The primary difference between the LCD2180WG-LED and just about any other LCD monitor on the market is not the 21in. LCD panel. Indeed, the LCD technology used here is a fairly straightforward, 1600x1200-resolution panel. However, instead of a typical defused fluorescent backlight to produce the light that shines through the panel and past those liquid crystals, NEC is using two strips of arrayed red, green, and blue LEDs (light emitting diodes).

Of course, at $6,749.99, this is no ordinary, off-the-shelf LCD monitor. At this point, the screen is geared toward a fairly specific audience. But if you're in that audience—a colorist, product designer, graphic artist, or member of another field where seeing true colors is critical—the LCD2180WG-LED might be exactly what you should be looking at today.

Without inputs for analog component video or SDI, however, the LCD2180WG-LED is certainly not yet ready for video reference monitor status, so editors will need to hang on to their bulky CRTs for at least a little longer. But if this month's CES show was any indication, we'll soon see LED backlighting in many different types of flat panels, including those that feature the proper video I/O.

Without inputs for analog component video or SDI, however, the LCD2180WG-LED is certainly not yet ready for video reference monitor status, so editors will need to hang on to their bulky CRTs for at least a little longer. But if this month's CES show was any indication, we'll soon see LED backlighting in many different types of flat panels, including those that feature the proper video I/O.

Some of the raw specifications of this LED-lit LCD monitor are rather underwhelming on the surface. NEC rates brightness at just 200 cd/m² and I actually measured no more than 122 cd/m², compared to 400-500 cd/m² for more ordinary, if premium, LCDs. Contrast is rated at 430:1, and I measured almost exactly that: 424:1. However, in this case, those are not the statistics that really matter. It's those wide color gamut numbers mentioned above.

A brighter white

If you can imagine the color depth that three-beam CRT projectors used to achieve by that blended red, green, and blue light, you'll start to appreciate what's (literally) behind NEC's LCD. By blending light beams of the pure primary colors, those projectors were able to create a pure and even white—and by extension a full range of grays all the way down to black.

Naturally, there's a big difference between those CRT projectors and a panel. That's because the LEDs themselves don't create the color, just the white light. The LCD panel still filters portions of the red, green, and blue light out of that white, thereby producing different shades of color. However, getting a full range of accurate colors is mathematically impossible if you start filtering or subtracting red, green, and blue from less-than-pure "white," and that's a common problem of typical LCDs backlit by CCFL (Cold Cathode Fluorescent Lamp).

If you don't start with 100 percent of white, you'll never achieve 100 percent of anything else. However, by combining pure red, green, and blue LEDs to produce something very close to pure white, an LED-backlit LCD can reproduce a fuller range of colors—even by the subtractive, or filtering, method used by LCDs. The result is a very steady and full range of grayscales with a consistent color temperature and very strong color reproduction.

In the NEC model, I found both primary and secondary to be very accurate, with the exception of magenta, which leaned toward blue. Green and red were actually outside the color gamut triangle on the CIE chart in my tests, although blue (almost always a difficult color) was inside and a little less saturated than ideal.

What's more, LEDs are solid-state devices that are individually programmable. That means you can calibrate the 2180WG-LED to the D65 white point or whatever variation of white best suits your workspace, source material, or output format in order to ensure the highest degree of color accuracy. And you can recalibrate the LEDs as necessary should the LEDs change over time, although that will happen a lot more slowly with LEDs than with a traditional CCFL.

NEC's onscreen menus offer seven different color-temperature presets, including sRGB and Adobe RGB, plus a programmable one that contains 12 individual adjustments: six each for the saturation and hue of the three primary and three secondary colors. For another $150 ($6,999.99 total for the LCD2180WG-LED-BK-SV version), NEC bundles the SpectraView Color Calibration Solution, including software and a GretagMacBeth Eye-One colorimeter. It's a great value if you don't have one already.

NEC's black box

Interestingly, the 2180WG-LED doesn't look much like a typical LCD monitor, either. Yes, it has a 21in. diagonal display area and a nice flat-panel front, but it isn't like the wafer-thin LCDs we've come to know and love. It's almost 5in. deep in order to accommodate the huge heat sink necessary for cooling for the hotter-than-fluorescent LEDs. In its black, boxy, and heavy (40lbs.) chassis, it's frankly not likely to win any style points. The base adds and additional 3.4in., although that footprint is really about the same size as that of a thinner LCD panel, so its thickness doesn't actually cost you too much desktop space. The base rotates to offer a vertical orientation, and swivels about 25 degrees off perpendicular.

The monitor has just two DVI-D inputs on the bottom rear of the chassis (one with eight-bit support, the other with 10-bit look-up tables), with no analog RGB or any other inputs. And if you're spending nearly $7,000 on a desktop monitor, it makes sense that you'd probably have or want to get a high-quality DVI graphics card that's capable of native 1600x1200 resolution (scaling is no better than average on other resolutions). There are no video inputs, like analog component or even SDI, and that's a little disappointing for video professionals. However, as I noted earlier, this is a 4:3 aspect ratio monitor and is not positioned as a video reference monitor.

Room to expand

Indeed, NEC does not take advantage of an LED characteristic that seems ideal for video: its fast duty cycle and ability to turn on and off between video frames. Nor is the 2180WG-LED a true High Dynamic Range monitor that can adjust backlight brightness in specific areas of the screen depending on the image being displayed. It is, instead, NEC's first and currently only LED-backlit monitor and, therefore, understandably starts with a more narrow focus on graphics and computer imagery reproduction. As such, it could hold great appeal for 3D animation studios. Its success, along with feedback from users, will likely determine when and if NEC expands the product line into other areas, like video.

If you're in the color business, or any design-oriented role where matching or creating specific colors is critical, the LCD2180WG-LED-BK is an obvious step up from a typical LCD and even your old faithful CRT. Is it worth the near $7,000 price compared to another premium LCD? That, of course, depends on your business, although NEC clearly doesn't expect this to be a mass-market product.

Other companies—like Samsung, Sanyo, and Sony—have publically demonstrated their own LED-backlit monitors and TVs, although none are yet available for purchase. Brightside Technologies does have a true High Dynamic Range LED-backlit 37in. LCD designed to handle the duties of a video reference monitor, but with a near-$50,000 price tag it, like the NEC, has an exclusive audience. Still, these are all first steps in a very exciting direction. The color gamut of LCD flat panels has been expanded, and your CRT is now officially on notice.

© 2009 Penton Media, Inc.