Plasma display panels: form over function

Sep 1, 1999 12:00 PM, Pete Putman

I recently completed an extensive test of six plasma display panels in my studio. Having now tested 12 different models in one year and after conducting a seminar on plasma technology at INFOCOMM '99, I sometimes sit back and wonder just what it is that has created such a fuss about plasma displays. I am reminded of Spike Lee in those old Nike commercials in which he asks what makes Michael Jordan such a spectacular athlete, "Is it the shoes? It must be the shoes!"

With plasma, it must be the packaging. We finally have an electronic display with which architects and interior designers can have some fun. Mount them horizontally or vertically. Fly them off the ceiling. Mix them into panels. Pump graphics and video into them. Build walls out of them. The possibilities seem endless, but are plasma display panels (PDPs) really the be-all and end-all of electronic displays?

Technically, PDPs exhibit several shortcomings that make them questionable choices to display high-quality video or work as multi-sync computer monitors. They are also fragile, and they must be handled with more care than comparable large-screen video or computer displays. Further, they are quite expensive for what they can do; are you prepared to spend upwards of $10,000 for what amounts to a wide-screen VGA monitor with limited ability to scale SVGA and XGA images? Even more expensive, 50 inch (1.3 m) XGA panels start just under $20,000.

Now, the upside. There are dozens of new display applications evolving every day simply because plasma panels exist. Imagine movie posters in which the image can change to show static scenes or short clips from the advertised film. How about dynamic signs in places of public accommodation, switching between airport terminal maps and flight arrivals and departures?

Yes, I hear you saying that all of that can already be done with direct-view monitors or rear-projection screens. The difference is that plasma display panels do not require as much room. For the first time, there is a video and data large-screen display available that requires less than 6 inches (152 mm) of depth, weighs 70 pounds to 120 pounds (32 kg to 54 kg) and can be wall-mounted, flown or installed in hide-away brackets with comparative ease.

As designers and installers, you will come up against the plasma mystique soon. You may already have customers who want plasma simply because it is plasma. The price may be no deterrent, and the idea of being able to free up precious floor space sounds good. These are plug-and-play devices, right? Just cable them up like any projector or monitor, hang them up, and you are in business.

To quote a recent car rental commercial, not exactly. The physical installation and cabling of plasma panels is indeed a plug-and-play scenario. They do not require much power - 120 VAC @ 3 amps to 4 amps is fine. Most models support the popular connector options, although several now use RCA jacks for component and RGB input, reflecting a consumer bias on the part of the manufacturers. There are hardly any adjustments to make - no convergence is required; just connect the sources and turn the panel on.

That is where the trouble begins. In terms of physical packaging and aesthetics, plasma panels have got it. They represent the next generation of futuristic displays we have expected for so long. In terms of performance, however, you get a mixed bag.

Plasma displays resemble CRT monitors in that they use color phosphors to create images. They also resemble LCDs in that they have a fixed matrix of imaging pixels and a native resolution. Because of the unique way they create images, plasma panels look best when they are fed a steady diet of RGB signals, preferably at their native resolution.

The catch is that there are few display applications - and drivers - available that can output 852infinity480 pixels or 1,365infinity768 pixels, to name two of the common plasma resolutions. This means that many computer images will appear as rectangular pictures with unused screen area left and right.

The alternative is to activate the wide mode on many displays, and anamor-phically distort the image by stretching it horizontally to fit the full 16:9 screen. Aesthetically, this may look worse as text and objects are expanded abnormally. Images of people appear grotesque when displayed this way. Yet, many dealers and manufacturers will actually set up plasma displays in this fashion for product demonstrations.

The obvious solution is to prepare all graphics for such panels with special computer display card drivers - if you can find them. ATI offers a driver for its Rage series cards that supports 848infinity480 pixels, but other manufacturers of specialty cards have yet to adopt this standard or, for that matter, any standard when it comes to wide versions of computer display resolutions.

Things get trickier with video. Arbitrarily stretching video images is not going to result in a satisfactory display solution for your client. The problem is further compounded by the low quality of most video scaling engines found in plasma panels, plus a problem known as false contouring or insufficient bit quantization.

False contouring is evidenced by abrupt changes in luminance across an image rather than smooth changes. These abrupt jumps up or down in brightness are most often observed with dark shades of gray, and they create a strong boundary between each level or false contour where there should not be one. Watching video from a DVD, a broadcast or even a videoconference reveals plenty of false contouring, a picture artifact that your clients may not want to put up with.

Letter-boxed videos present even more of a challenge. Although their picture aspect ratios are close to 16:9, they will appear as little band-aids on 4:3 images, which themselves do not fill the screen. Several panels incorporate zoom or wide functions that will digitally enlarge video to fit the screen width and height, but they also expand the line and pixel structure of the video signal. The end result is a soft image that is often pixilated and aliased.

Most savvy manufacturers use HDTV programming to demo plasma panels at trade shows and dealer showcases becuase 1,920infinity1,080i HDTV signals already fit the 16:9 picture area, and they have more resolution than the panel can handle, almost 50% more with 852infinitry480 panels. The resulting images undergo light scaling compression, but they still look far better than conventional video. The only problem is where do you get HDTV sources?

Plasma panels are also starting to show evidence of a problem not seen since early CRT monitors were developed - phosphor burn-in. Four of the panels I tested had burned-in images after only a couple minutes of displaying Windows screens and image adjustment menus. One model has a dynamic picture mode that boosts brightness even higher and intensifies image burn-in.

Based on my tests, plasma panels can output as much as 70 nits brightness, and all but one of the review models exceeded 150:1 contrast. That is comparable performance to a 27 inch (686 mm) or 37 inch (940 mm) CRT monitor and bright enough for most public venues or conference rooms using fluorescent lighting. Feed these panels a steady diet of evenly lit RGB images, and you will have a top-notch display solution. Indeed, many current applications of plasma are in dynamic signage, replacing film transparencies used for advertising.

Other logical places for plasma displays would be any retail location where floorspace is at a premium. Look for videowalls to be constructed from plasma panels in the near future, conserving even more room for store displays. Open atrium malls are also a natural for electronic signs using plasma; their wide viewing angles and legibility in high ambient light help catch the eyes of passersby.

The size of plasma panels appeals to designers of boardrooms and conference rooms who want to hide screens when not in use. One installation I saw in a major city hospital has six 42 inch (1.1 m) panels emerging on drop-down brackets from an acoustic drop ceiling for distance learning and continuing education. Other installers have built plasma panels into the walls of conference rooms, putting up still images of floral decorations, scenery and even tropical fish when the panels are not in use.

Trade show booth designers have taken to plasma. At NAB this year, several booths featured dozens of plasma panels arranged outside to draw customers in, and inside to showcase product features and show short video demos. At one booth, I counted 40 separate 42 inch panels around the outside edge. By using solid RGB colors, mosaics or panels can be created that quickly transition into graphics, photos, text or even video and film clips. In this fashion, the panel becomes part of the booth's color scheme.

How hard would it be to replace the menus at a fast food restaurant with plasma displays? Not at all, and those same panels could be used to show a mouth-watering lunch to patrons standing in line. They could promote contests. Quick-mart stores could also install plasma screens to showcase different products at different times of day - hot coffee and pastries in the morning, sandwiches and hot dogs at lunch and snack foods the rest of the day.

In the home theater business, plasma is not ready to show quality video without the help of third-party digital video scalars, products invented to solve video quality problems on LCD projectors that are now riding to the rescue of plasma displays. I have tested both high-end models and low-end designs, and both make a big difference in video quality. Indeed, several scalars announced at INFOCOMM either come integrated with standard plasma resolutions built-in or include user-programmable memories for setting pixel counts.

If you are one of the many people who have fallen under the spell of plasma, do yourself a favor and ask for an extensive demo with every possible signal source. Make sure your client sees this demo as well. This way, you can marry form and function in a satisfying way, taking advantage of all the unique installation options that a plasma display can offer.

Remember that plasma displays are still in their infancy. There is no doubt that their performance will improve in quantum leaps over the next few years. In the interim, custom computer video cards, careful selection of video and data images and digital scalars will get you over the bleeding edge.