Archive for Wednesday, July 15, 2009

New LCD TV tech can enhance performance

July 15, 2009


While TVs continue to get larger and prices continue to shrink, the best news is that picture quality keeps getting better — not by leaps and bounds but in small steps that add up to noticeable change over time.

According to the editors of Consumer Reports, one reason is that new technologies, such as 120Hz refresh rates and LED backlights, help LCD sets overcome traditional weaknesses, providing an enhanced viewing experience.

Thanks to improved picture quality, 21 of the 25 models CR recently tested were recommended. Yet while LCD TVs have made great strides, many still suffer from a fairly narrow viewing angle, where the picture can deteriorate when viewed off-angle. A handful of LCD sets had a very good viewing angle, but many still require the viewer to sit directly in front of the set to enjoy optimal picture quality.

Improved black levels

All LCD displays use backlights, usually fluorescent lamps. In an LED backlight, solid-state devices called light-emitting diodes take the place of lamp tubes, and offer better color and more controllability in the brightness.

Some new models, like the 55-inch Samsung LN55A950 ($3,600) and the 46-inch Sony Bravia KDL-46XBR8 ($3,500) — both top-rated sets — use “full-array” LED backlights instead of lamps. This type of LED backlight runs across the entire back of the panel. By dividing the backlight into small segments that can be controlled separately — a process called localized dimming — some parts of the screen can go dark while others remain illuminated. CR’s tests found these full-array LED backlights can improve black-level performance in very dark scenes, creating a better overall contrast.

LEDs are more costly than fluorescent lamps, so some TVs have fewer LEDs. These models use “edge-lit” LED backlights, which are placed around the perimeter of the frame; diffusers are used to distribute light across the entire panel. CR found that while edge lighting can help manufacturers reduce the depth of a set, creating very thin (1.5-inch), aesthetically pleasing designs, it doesn’t allow for local dimming. As a result, sets with edge LED backlights didn’t enjoy the same degree of black-level improvement as those that used full-array LED backlights.

Less motion blur

Many new models now feature 120Hz technology, which can refresh images 120 times per second, rather than the usual 60 times per second. Of the 25 sets CR tested, 11 sets (all 37 inches or larger) had this feature. This feature can help reduce motion blur, or the smearing of images, during fast-moving scenes, a traditional LCD TV weakness. This flaw is most obvious with test patterns, but might be visible when viewing movies and TV programs, such as sports, that contain fast-action scenes. On most sets with the 120Hz feature it is combined with a “motion smoothing” feature that reduces the jittery look of movies. This combination can be turned off, as some viewers feel it can make film-based content look uncharacteristically smooth, or too video-like.

Manufacturers are already moving beyond 120Hz technology to address the issue of motion blur. Samsung and Sony, for example, recently introduced 240Hz TVs that actually quadruple the frame rate. LG, Toshiba, and Vizio try to create the same effect by combining 120Hz technology with a scanning (flashing) backlight.

Internet connectivity

TVs continue to add new features, such as access to Internet content from select partners. A handful of models let you stream movies, videos, photos, music, as well as news, sports and weather updates, from various Web sites. New models from Samsung and Sony (soon to be joined by LG and Vizio) feature onscreen Internet “widgets,” using a platform created by Yahoo. These widgets let viewers access Web-based services — such as YouTube videos, movies from Netflix and Amazon on Demand, and digital photos stored on Flikr — directly from the TV without connecting to a PC. Among the LCD sets tested by CR, the Samsung UN46B7000, $2700, has widgets.


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