How to Choose a Flat Panel Page 2

Not all sets with LED backlighting use local dimming. This is still an expensive feature you’ll find on premium sets, but display manufacturers have more tricks up their sleeves. Some LED-backlit sets that don’t employ local dimming produce deeper blacks by dimming the entire LED backlighting array in dynamic fashion, but the result isn’t as effective as zone-based local dimming. Some LED sets are edge-lit designs in which the LED lighting is arranged around the sides of the screen. Edge lighting requires fewer LEDs than full backlighting, uses less energy, and allows for those iPhone-thin, sexy designs.

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While LED edge-lighting can improve a set’s form factor, it doesn’t necessarily mean improved performance. Edge lighting can sometimes produce an unevenly illuminated image. Fortunately, this isn’t visible on most program material, but it can appear in bright areas of white or uniform color. Full-screen blacks might also have a mottled, streaky appearance. These problems can also occur with full backlighting, although this is less common. All back or edge lighting requires some form of diffusion to spread it evenly across the screen, and non-uniform illumination can usually be traced to less-than-perfect diffusion.

Yet another LED refinement in some sets is dynamic/precision dimming in an edge-lit design. Our early impressions are that this can provide a definite improvement in blacks and contrast and in at least one instance, fewer uniformity issues than other edge-lit designs. But again, not all edge-lit designs have dynamic dimming technology.

Need for Speed
LCDs have also long been inferior to plasmas in their response to fast motion. To reduce this problem, many LCD sets now operate at a frame refresh rate of 120 Hz. In order to reproduce a 1080p/24 source at the set’s 120-Hz refresh rate (1080p/24 is almost universal for movies on Blu-ray Disc), the set must add four new frames for each real frame (24 x 5 = 120). It can do this in one of two ways; it can either repeat frames or interpolate new frames using the preceding and following frames as a reference. The interpolation route can produce dramatically smoother motion. There are also sets that go this one better, with a 240-Hz refresh rate. Some of these 240-Hz sets use a genuine 240-Hz refresh rate, while others use a 120-Hz refresh rate that’s supplemented by a scanning backlight to simulate 240 Hz. Some sets with a true 240-Hz refresh also add backlight scanning to bring this up to an effective rate of 480 Hz.

While the frame interpolation used for these 120-, 240-, and even 480-Hz features can greatly smooth a set’s response to fast-moving images, it can also make filmed sources look like video. Some video enthusiasts (including HT’s editor and senior editor) strongly dislike this quality. Fortunately, most of these sets let you dial back the interpolation or shut it off completely.

The picture quality of most LCD sets also degrades substantially when you view them from significantly off axis. Even at 20 to 30 degrees to the side, the image can begin to look faded and discolored. Most LCDs typically specify viewing angles that approach 180 degrees. You can still see an image at nearly this angle, but this kind of spec is invariably wishful thinking when you take image quality into consideration.

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Plasmas aren’t free of issues, either. Plasma screens can retain shadowy ghosts of previously displayed still images, either as temporary image retention or permanent burn-in, depending on the prior image’s brightness and how long it remained in place. This susceptibility is most pronounced when the set is new, with less than 200 hours or so of use, but it never disappears completely. A reasonable amount of caution is always wise with a plasma set when you’re viewing still images or content that has some stationary elements, such as video-game score boxes. While paranoia is uncalled for, you don’t want to leave such images on a plasma screen for an extended period.

Plasmas can also use more power than LCDs, although plasma makers dispute this, referring to ENERGY STAR data to substantiate their claims. They also offer less brightness than LCDs. This can put plasmas at a disadvantage on the bright showroom floor, but it’s rarely a significant disadvantage at home.

Internet Apps
Yes, flat-panel HDTVs are now Internet-connected devices that run widget-based apps. From most of the major manufacturers, the app packages are more similar than different. Streaming video content apps from Amazon, Blockbuster, and VUDU are prevalent, as are music-based apps like Pandora Internet radio (which seriously rocks—the thing practically reads your mind). Netflix’s video streams are limited to 720p and stereo audio, which makes it inappropriate for serious movie watching. If you’ve got the bandwidth, VUDU steps up the streaming game with near Blu-ray-quality 1080p streams with Dolby Digital Plus 5.1-channel surround at up to 648 kilobits per second, which is a higher data rate than we used to get from DVD. But that’s hardly all. Some HDTVs are coming with Skype video-calling apps and offer accessory cameras, and there are a variety of photo viewing apps out there. Convergence has finally found its footing and no longer requires a full computer interface to provide meaningful Internet applications. Any HDTV you look at will have a list of the apps it includes.

Shopping Tips
For shopping comparisons, try to find a store that offers a room with subdued lighting. You should bring some of your own discs, particularly ones that have dark, difficult scenes. Stores love to demonstrate HDTVs with colorful computer animation and scenes of bright, cheery beaches on sunny summer days. Those images look impressive on almost any decent set. But it’s the dark, live-action scenes that will help steer you to the best HDTV.

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When you test an HDTV, stand back at roughly the same distance you plan to watch from at home. Grab the remote if you can and switch out of the Vivid or Dynamic mode (that’s where it will almost certainly be set) and into Cinema or Movie mode instead. However, some Cinema or Movie modes look wrong, too, particularly if the designer was looking for a soft, gauzy appearance that he or she thought was appropriate for films. If that’s the case, try the Standard mode. Turn down the Sharpness control until the edgy, unnaturally enhanced look disappears. If this takes you to a sharpness setting of zero, don’t be alarmed. On many (but not all) sets, zero sharpness is actually optimum.

The dimmer modes will look odd at first, particularly next to the sets around it in the store, which will still be in Vivid. But give them time. Don’t rush. Shopping for an HDTV may not be at the top of your list of fun things to do on the weekend. However, if you’re a three-hour-a-day TV watcher and use the new set for 10 years, you’ll spend over a year of that time in front of it. It’s worth a little effort to find the one that’s best for you.

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