Felix Torres
07-05-2006, 03:00 PM
Plasma Display Panels are the ‘tweeners of the HD world: stuck in between the high-volume small-size LCD displays and the low volume, large size micro-display rear projection markets, and getting squeezed by both. Some think it is a doomed technology—it isn’t. It's just…misunderstood by both its detractors and its supporters.<br /><br />Technology-wise, PDPs are an oddity in that their core technology doesn't come from the semiconductor industries like DLP and the various LCD variants, but rather from the analog TV industry. And where the others are transmissive or reflective technologies that rely on separate light sources, PDPs are <b>emissive</b> and produce their own light. Most of the science behind these displays has its roots in the earliest B&W CRT displays. As a result, in the PDP marketing world the term HD doesn't mean the same thing it does elsewhere, particularly when it comes to resolution. In the analog TV era and especially the B&W days, horizontal resolution was not a critical design element; you didn’t design for a given resolution—you took whatever you could extract from the received broadcast signal and what you got is what you got. Even after the advent of color and stripe-based displays, analog TV designers never bothered much with the horizontal resolution of a display - that was strictly a concern of the computer monitor manufacturers, not the designers. As a result, most consumer-grade CRT TVs are rated by their lines of resolution (usually 600 for the low and mid-range, 800 for the better displays) and any attempt to divine the dot-pitch of a TV tube (and hence its horizontal resolution) usually gets blanks stares or is just shrugged off.<!><br /><br />PDP manufacturers seem to share this lack of concern over horizontal resolution and their customers don’t seem to mind at all. As recently as mid-2005 over half the PDPs sold were ED, not HD TVs, and of the ones billed as HD, an unspecified but significant (over 50%?) fraction are actually 1024x768 stretched XGA, rather than native HD displays. This does <b>not</b> hamper sales. Indeed, it is not uncommon to hear from PDP proponents that ED image quality is <b>better</b> than HD. (They have a point, too, but not the one they think).<br /> <br />PDP buyers just take what they can get and are happy to do so. Indeed, if you look carefully at recent sales data (2005), it becomes apparent that 90% of all PDP sales are for just two sizes, 42" and 50". If you're looking for HD-native resolutions, you're most likely looking at 50"+, as most of the 42" models are stretched-XGA, not 720p-native. <br /><br />Which is to say, size-wise, PDPs don't offer consumers much choice.<br />What they do offer is the most CRT-like image quality among HD displays, and some tend to think of PDPs as "flat CRTs", which isn't technically accurate. PDPs create their images by indirectly stimulating a glowing phosphor layer instead of direct stimulation, as CRTs do—but it does reflect the "flavor" of the displays pretty accurately. For a real “flat CRT” display, we’ll all have to wait for the mythical SED flat panels, if they ever do get to market this decade. Their expected ‘06 arrival has recently been pushed back at least a year.<br /><br />The CRT-like nature of PDPs is both the source of their strengths and weaknesses. Consider that PDPs generate their images by electrically exciting a low pressure gas into a high-energy state of matter, called a Plasma. This then causes it to emit ultraviolet photons that in turn stimulate a layer of phosphors to emit visible-light photons—somewhat like fluorescent bulbs do—which then go through a colored filter layer to produce a visible, colored pixel. While PDPs are fixed-pixel digital displays at the panel level, the individual pixels are basically analog in nature—the intensity of the ultraviolet glow can be controlled with great precision so that each sub-pixel channel can have a different response curve. A very nice attribute. The price of this? It takes a <b>lot</b> of energy to excite a gas into a light-emitting Plasma; hence PDP's reputation as high power-consumption devices. Current PDPs aren’t as bad as early models, though, and they only average about 300-350 watts. A second side effect is that the phosphors being excited by the hot Plasma degrade with time and that degradation is a function of the power being applied. The higher the stimulation, the brighter the image, the faster the phosphor degrades. Current phosphor formulations have good half-lives (the time it takes for the panel to lose half its initial maximum brightness) of over 10 years of normal usage.<br /><br />PDPs do offer the <b>best</b> pixel-to-pixel contrast and the best black levels of current (2005-06) HD displays. This is due to the presence of—indeed, <b>need</b> for—dark barrier ribs separating the individual sub-pixel gas cells, that are analogous to the shadow mask that defines the pixel borders in CRT displays. It is these necessary barrier ribs that constrain PDP panel sizes and limit manufacturers’ ability to increase resolution or reduce HD panel size below 42”. With other HD display technologies, there are no physical sub-pixel borders (microdisplays) or the inter-pixel area is very small compared to the lighted screen area (LCOS, direct-view LCD). Not so with PDPs, where the barrier ribs are structural in nature and are needed to maintain the integrity of the sub-pixel gas cells, so a certain portion of the screen area will always be unable to generate an image, resulting in the well-known screen door effect that requires viewers to stay beyond a certain viewing distance to avoid detecting the inter-pixel grid. These barrier ribs prevent light leakage from one pixel to the next—hence PDP's point-to-point contrast excellence—but they also consume surface area, reducing the maximum amount of light the panel can display. Hence, PDPs have the lowest full-screen brightness of the competing technologies. And, because the percentage of panel area consumed by the barrier ribs goes up with resolution, panel brightness goes down with resolution. <br /><br />This, folks, is why many Plasma connoisseurs say that ED is better than HD—at least with PDPs: with less pixels in the same surface area, each pixel is bigger and hence brighter (more emissive area), so pixel-to-pixel contrast is higher and full-panel brightness is higher. Plus, the panels are easier to manufacture and are likely to be cheaper.<br /><PAGEBREAK><br /><span><b>Continued...</b></span><br />Another side-effect of the barrier ribs is that, like a CRT shadow mask, they present an absolutely black backdrop for the image being generated so large expanses of black are exactly that - solid black, not 99.9999% black as in LCDs and micro-displays. Put another way: PDPs are the best there is at generating a blank screen. This is great for black levels; less-so for other colors, as it produces the well-known screen door effect mentioned above.<br /><br />Finally, there is the well-known—and generally misunderstood—matter of image retention. Yes, even modern PDPs exhibit image retention. No, it is <b>not </b>permanent or fatal under normal video usage. Note the qualifier. Image retention is the result of individual pixel phosphors being continually excited to a constant level. Think of it as sort of a form of elasticity - you stretch a rubber band and let go, then it comes back to its normal length. You hold it long enough in the stretched mode, it doesn’t come back quite all the way. Do it long enough, often enough, and the rubber band will be noticeably longer than one that wasn’t so abused. So it is with PDP phosphors: with normal video content—movies, sporting events, talking heads, etc—the phosphors are stimulated to a constantly changing degree that over times averages out about the same for all pixels. With the result that phosphor excitation is pretty much uniform across the panel, no image retention occurs. Of course, non-video content—computer desktops and GUIs, text-crawler bands on news channels, video game HUDs and borders, and other digitally-generated imagery—can and does result in temporary image retention. <br /><br />Modern PDPs have all sorts of tricks to minimize this effect (shifting the image by one or two pixels around the panel is one technique) but it is still there and with modern phosphors it is mostly a temporary inconvenience until normal video “scrubs” the panel back to normal. However, temporary or not, it still happens, so Windows or Mac desktops, XBOX 360 Hexic, card games, etc., are not good candidates for marathon sessions on PDPs if you are easily freaked out.<br /><br />Now, display technology issues aside, how do HD PDPs stack up in the evolution of TV viewing?<br /><br />Well, first of all, HD PDPs do not scale <b>down </b>well. They are not now, nor are they likely to be available anytime soon in under 40” sizes, so that whole segment—the bulk of the business—goes, by default, to LCDs, regardless of their virtues or faults.<br /> <br />Second, PDP price, mass, and power usage goes up significantly with screen size so don’t expect to see volume sales of cheap 70” PDPs this decade. It might happen, but in general, we can safely assume the 60”+ segment will be dominated by micro-display rear-projectors just on the strength of their scaling economics, as they can easily undercut PDPs by 50% at the 60” level and it gets worse as you move higher.<br /><br />Finally, and most controversially, because PDP sub-pixel cells does not scale down well, resolution becomes an issue. Until late '05 it was believed that 1080p PDPs smaller than 60" were not economically viable, but Panasonic performed an engineering tour de force by demonstrating a 50" 1080p panel that should ship in the second half of '06. For all that, smaller 1080p PDPs should not be expected any time soon, and definitely not at the volumes and prices of 1080p LCDs. Do <b>not </b>expect to see anything higher than straight 720p resolution at 42” and do <b>not </b>expect to see 1080p at anything smaller than 50”. (Remember: brightness is a function of pixel size with PDPs, so increasing resolution requires both smaller pixels and getting more light per unit area out of each pixel).<br /> <br />As for Quad-HD native resolution, the next step in micro-display and LCD evolution? Sorry. Not in the cards. 1080p is almost certainly as high as PDP tech goes this decade. After that, SED or OLED had better be ready to pick up the emissive-display baton because otherwise the race is over.<br /><br />Now, unlike some in the mass media, I don’t think PDP tech is doomed to extinction. Not with Matsu****a/Panasonic furiously pumping money into the technology. But…<br /><br />PDPs are currently only manufactured in volume by five companies, which together account for 99% of all the displays sold. Fujitsu, Samsung, and LGE are merchant suppliers, so most of the second tier vendors get their panels from them. Panasonic and Pioneer produce panels for in-house use only, with one or two partners on OEM basis—full displays, not component sales. And, while Panasonic has been very aggressive in expanding capacity, others have been less so. Pioneer actually reduced capacity in '05.<br /><br />In the second quarter of 2005, total sales were divided as follows:<br /><br />Samsung 29.1%<br />Matsu****a 24.8%<br />LGE 23.7%<br />Pioneer 12.3%<br />Fujitsu 9.4%<br /><br />Overall growth was 11% quarter-to-quarter, mostly due to Panasonic’s increase in production capacity - a healthy, profitable business.<br /><br />PDP economies of scale project to decent sale price reductions over time, but nothing like the dogfight expected in the LCD arena. Typical panel pricing is expected to follow the following trends:<br /><br /><b>HDTV name-brand display pricing, US$</b><br /><img src="http://www.digitalmediathoughts.com/media/users/634/Part%205%20-%20table%201.gif" /><br /><br />Overall, PDPs seem to be competitive in their size range, no? Except that most of the rear-projection units and direct-view LCD displays they will be competing against after '06 are going to be 1080 models, not 720. <br /><br />That is going to hurt some.<br /> <br />Volume-wise, the PDP business will likely lag the explosive growth of LCD TV, simply because the bulk of future HDTV market growth lies in the under 42”, CRT-replacement business and the nearest CRT-equivalent to the PDP bread and butter 42” is the 32” model, which accounts for something like 12% of the existing installed base. So, unless a lot of folks get a hankering to move up two display sizes from their previous set, without a big resolution boost, the best PDPs can hope for, cost-issues aside, is for a one-eighth slice of the overall HDTV pie. Nice, but hardly comparable to the 2/3 market share expected for the LCDs.<br /><br />Theoretically, one could argue that PDP manufacturers can drop prices faster than they currently are and that they can deliver true 720P 40” panels at 3LCD MD prices if they feel the need for it. If they physically can, they should. And soon. Because, otherwise, they face a highly competitive environment with one hand tied behind their backs.<br /><br />Best guess here, is that the PDP business grows nicely, prices drop steadily but not dramatically, resolution improves gradually—true 720p replacing ED and stretched-XGA in the 42” products and 1080p replacing WXGA in the over-50 market, with a few thousand 65” models a year at the high end for the connoisseurs—creating basically a two-and-a-half product business. <br /><br />Add it all up and the answer screams: niche product!<br /><br />Indeed, if you look at the five top PDP panel vendors, you see that the only one of the five that <b>isn’t </b>selling HD PDPs as a premium-priced, connoisseur-only premium product is Panasonic. Yes, MAXENT and DELL and others offer low-priced PDPs. But that isn’t where the category <b>volume</b> lies. The future of PDP lies at the higher end.<br /><br />One can even argue that PDPs don’t sell into the TV market at all. Their true market is as a low-end Home Theater product, not a TV-viewing product and that a proper comparison for PDPs is not rear-projection MDs and LCD flat panels but, rather, front-projection Home Theater systems. Certainly the viewing environment and viewer profile is a lot closer to the latter than the former.<br /><br />PDPs are great for certain uses, certain users, but for common, ordinary TV use in the HD era they just don’t match up well with the way the market is evolving (smaller, cheaper screens, 1080-content, one-to-pixel mapping, gaming and other computer-generated imagery,etc). What PDP <b>does </b>match up well with are Home Theater enthusiasts, where the alternative to a PDP is a front projector. <br /><br />It may <b>also </b>be your display of choice if the bulk of your display use is watching movies and TV under controlled viewing conditions—distance, lighting, display calibration just-right. If you don’t play games with static screen elements for extended periods of time, if either 42” or 50” is just right for you, if you <b>truly </b>intend to wall mount your display (only 29% of flat panel buyers do so, BTW), or if you literally don’t care about HD resolution and one-to-one pixel mapping at all.<br /><br />Individually, those are not terribly big individual niches, but collectively they do sound like a healthy 12% cut of the future-sized market. PDPs are <b>not </b>going to die, but <b>neither </b>are they going to <b>define </b>HDTV much longer. <br /><br />What mainstream consumers <b>want </b>and what mainstream consumers are <b>going </b>to get lies elsewhere; LCD and MD, mostly.<br /><br /><b>Next up:</b> Penultimate chapter—the resolution wars!<br /><br /><i>Felix Torres is a dabbler in home entertainment electronics and a survivor of both the home computing wars of the 80's and the multimedia wars of the 90's who is currently most interested in home media networks and the North American transition away from broadcast media. </i>