I feel the need to revisit a topic that I've already written about. In this case, the subject is HDTV resolution, and 1080p resolution in particular. This seems to be on everyone's minds as we approach the Sky HD launch and we're faced with more HDTV buying choices than ever before. Not a day goes by without someone asking whether they should just buy a "standard" 720p/1080i set or step up and pay the extra cash for a higher-resolution 1080p set. Or what it all means. And so, I've tried to condense the whole discussion into a neat, little cheat sheet. Read on for the quick and dirty lowdown on 1080p.

 1. 1080p defined
1080p resolution--which equates to 1,920x1,080 pixels--is the latest HD Holy Grail. That's because 1080p monitors are theoretically capable of displaying every pixel of the highest-resolution HD broadcasts. On paper, they should offer more than twice the resolution of today's 1,280x720, or 720p, HDTVs. Some companies, such as LG, refer to these super-high-res of sets as ultra-HD, while others prefer to substitute true or full for ultra.

 2. Why 1080p is theoretically better than 1080i
1080i, the former king of the HDTV hill, actually boasts an identical 1,920x1,080 resolution but conveys the images in an interlaced format (the i in 1080i). In a tube-based television, otherwise known as a CRT, 1080i sources get "painted" on the screen sequentially: the odd-numbered lines of resolution appear on your screen first, followed by the even-numbered lines--all within 1/30 of a second. Progressive-scan formats such as 480p, 720p, and 1080p convey all of the lines of resolution sequentially in a single pass, which makes for a smoother, cleaner image, especially with sports and other motion-intensive content. As opposed to tubes, microdisplays (DLP, LCoS, and LCD rear-projection) and other fixed-pixel TVs, including plasma and LCD flat-panel, are inherently progressive in nature, so when the incoming source is interlaced, as 1080i is, they convert it to progressive scan for display.

 3. What content is available in 1080p?
Really, nothing at this point. Today's high-def broadcasts are done in either 1080i or 720p, and there's little or no chance they'll jump to 1080p any time soon because of bandwidth issues. Meanwhile, some newly announced DVD players from Denon and NeuNeo (who?) are claiming to upconvert standard DVD movies to 1080p resolution, but that's a far cry from native high-def content. More promising is the post-DVD future. There's been a lot of chatter over whether the new breed of high-def movie players, Blu-ray or HD-DVD, as well as the upcoming Sony Playstation 3, will output in 1080p. Allegedly, they will, but those players and recorders will be very expensive at first, and they probably won't hit more modest price levels until 2007 or even 2008. The PS3, on the other hand, is designed to be more of a mainstream product; we hope that means a price tag in the neighborhood of £300. It's unclear, however, exactly what it will output in 1080p--games, Blu-ray movies, or both--or neither.

 4. How much extra does a 1080p TV cost
Not surprisingly, you'll initially have to pay a premium to get the latest and greatest technology. If you take a look at the product lines of Sony, Samsung, and Mitsubishi, you can see that, on average, you can expect to pay about at £600 extra for the bump in resolution. Eventually, of course, the gap will narrow, but it'll take a couple of more years for 1080p displays to become the standard.

 5. Why you should buy--or not buy--a 1080p set
While I havent read many review for 1080p sets, I have read about some US sets, some of them are early, nonshipping units. These include HP’s MD6580N, a 65-inch 1080p DLP, and Sony’s KDS-R60XBR1, a 60-inch LCoS (SXRD) set that brings the technology from Sony's highly regarded Qualia 006 down to a more-affordable price point. After seeing 1080p in action, I’ve come to some conclusions.

Obviously, the quality of the source material you're viewing is very important, but so are screen size and how far you're sitting from your TV. Indeed reports that the extra sharpness afforded by the 1080p televisions that have seen is noticeable only when watching 1080i sources on a larger screen. Comparing a 50-inch 1080p DLP set to a 50-inch 720p DLP set, for example, you'll be hard-pressed to notice more detail with 1080i sources, especially from farther than 8 feet away. Even if you can see the difference, it will be much less obvious than, say, the difference between DVD and 720p HDTV. Of course, performance will vary from set to set, and we'll know more when everyone has a chance to thoroughly test more 1080p televisions.

Others also say that the main real-world advantage of 1080p is not the extra sharpness you'll be seeing, but instead, the smaller, more densely packed pixels. In other words, you can sit closer to a 1080p television and not notice any pixel structure, such as stair-stepping along diagonal lines, or screen door effect. This advantage applies regardless of the quality of the source.

Another thing to consider: even if the display has a native resolution of 1080p on paper, it can't necessarily display all 2 million-plus pixels in the real world. For example, the Sharp LC-45GX6U, a 1080p 45-inch flat-panel LCD, actually wasn't as sharp as it claimed to be; it couldn't resolve every line of a 1080i-resolution test pattern.

Finally--and this may sound weird--but many 1080p televisions don't accept 1080p sources at all. In our experience, only the aforementioned HP can handle 1080p via its HDMI inputs--all other current 1080p HDTVs cannot. Instead, they upconvert 720p and 1080i sources to 1080p.

Oh, and I would be remiss not to mention computer connectivity. Those of you thinking of running your PC through a 1080p set should be aware that you may not necessarily get to use all that extra resolution--even if you have the right high-end graphics card. For instance, the Sharp set allows you to max out at only 1,280x1,024 resolution while the less-expensive Westinghouse LVM-37W1, along with Samsung’s 1080p RPTVs and one series of high-end sets from Mitsubishi, accept true 1,920x1,080 resolution from a PC. I expect most 1080p HDTVs announced in 2006 to handle 1080p sources, but for now, that capability is rare.

The bottom line: if you're thinking of going big, really big (a 60–inch screen or larger), the extra resolution may make it worth the difference--as long as you have a pristine, 1080i HD source to feed into the set. As to whether true 1080p sources from PS3, a Blu-ray deck, or an HD-DVD player look better--we'll have to wait until late 2006 to find out. Of course, it's probably a good idea to buy--or wait for--a set that can accept a 1080p signal so that you'll be able to make that judgment.