Courtesy of HD Guru
Shoppers have all kinds of choices to make when it comes to buying an HDTV.
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updated 11/15/2011 3:38:38 PM ET 2011-11-15T20:38:38

Some really terrific large-screen HDTVs are available today. Properly adjusted and viewed from the right distance in low ambient room light, the image quality can be amazing.  However, unless you assess and optimize home viewing conditions you will not be able to see the extra performance that can justify the cost of the best big-screen sets. These top sets, with 65-inch to 70-inch screens, cost between $3,000 and $8,000.

Our checklist will help determine if your viewing conditions will allow you to see the picture quality these sets provide. If not, HD Guru recommends sets that are priced lower. You won’t notice a difference on the screen, but you will in your wallet!

Seating distance: Size vs. your eyes
Choosing a set that’s sufficient for your needs requires some basic decisions about screen size and budget, since one directly affects the other. Most buyers have screen size limitations based on set placement requirements such as available wall space or cabinet size.

Our viewing distance chart shows how close you must be to a given screen size to resolve all 1,080 lines of resolution delivered by 1,080p sets.

If you sit farther away, use the chart to see if that distance matches the 720p viewing distance. Once your viewing location exceeds the 720p resolution distance, other factors such as motion blur and fine detail reproduction become unnoticeable. Why pay for performance you sit too far away to see?

We recommend choosing a screen size that allows seeing full high definition at your preferred or required viewing distance. The typical 9-foot viewing distance found in most homes equates to a 70-inch screen, though this size is more expensive and/or larger than most people desire or their furnishings can accommodate, so use that as a rough example.

Room lighting: How's the contrast?
Too much light in a room can make it hard to see the TV.

“Black level” refers to how close to zero the brightness of black measures. “White level” refers to the maximum brightness of white a set can deliver when the controls are optimized. The difference between the two levels is the set’s “contrast ratio.” The greater the ratio, the better the perceived picture quality. Sets with higher contrast ratios are seen as having more detail and “crisper” images.

Perceiving a set’s maximum contrast ratio necessitates a very dark viewing environment. At .004 ft lamberts, Panasonic’s TC-P55VT30 produced the lowest black level we’ve yet measured.

However, you will not notice the superior “inky” blacks produced by this set compared to one that is not capable of producing such deep blacks if you view both simultaneously in a room with high ambient light. In low ambient light, LED LCD sets featuring “local dimming” can make portions of the image appear almost dead black.

Sets with superior white level performance tend to not look washed out when viewed in higher ambient light conditions. LCDs can be cranked to brighter levels than plasmas.

In bright, daytime viewing conditions in a room with many untreated windows, sets capable of producing bright white levels but not deep blacks will look about as good as sets capable of deep blacks that usually cost more.

Plasma TVs have more than adequate brightness for typical rooms. The extra brightness produced by LCDs will be beneficial in rooms without shades or curtains and used mostly for daytime viewing.

Conversely, bright rooms negate the benefit of TVs with exceptionally deep black levels, such as LED LCDs with local dimming backlights (i.e. Sony HX929, Elite LED, LG 55LW9800) and plasmas.

Lower-end LCD models fit the bill for very bright rooms. Samsung’s LN series tops out at 46 inches, while Sony’s go up to 55 inches. LG and Sharp offer LCDs as large as 60 inches. These all feature 120 Hz refresh rates, which is fine if your viewing distance is beyond the 1080p maximum for your size screen, because you are unlikely to see a motion sharpness improvement with a more expensive 240Hz refresh rate set.

Viewing position: What's your angle?
Viewing angle is how much you can see when you're seated to one side or the other, rather than facing a TV dead on. Determine the maximum viewing angle in your home, based on your seating. Then check those angles at the store when you audition sets you are considering to buy, in order to see if the picture holds up at that the widest angles.

Plasmas and LCD off-axis image quality differs greatly, with plasma sets capable of covering a far wider area with very low contrast loss and no color degradation. By comparison, LCDs (including LED based LCDs) have a far narrower viewing angle in both the vertical and horizontal planes, though some sets perform better than others.

Plasma’s wider viewing angle advantage is of consequence only if more than a few people are watching and from various off-axis vantage points. On-axis, both types of displays will appear relatively similar. Off-axis, plasma picture quality will appear virtually unchanged while the LED contrast ratios drop, producing a flatter picture, with darker whites and lighter blacks.

If you want require a wide viewing angle, go for plasma, though the IPS panels found in many lower-end LG and Panasonic LCDs and LED LCDs tend to have a better viewing angle than other LCD panels. Other factors come into play here, so results may vary.

Summary: Don't buy more TV than your living room can handle
We always recommend the largest set you can fit and/or afford, if you can’t meet the viewing distance screen size guidelines we’ve outlined. If you are sitting at the 720p viewing distance or beyond, consider a set with that resolution. 720p plasma sets are available in screen sizes up to 51 inches. (All over-32-inch LCD sets sold today are 1080p.)

If you want to view the TV in daylight, but have large windows and don’t want window treatments, consider LCD sets. The brighter the room, the less important black level becomes. Meanwhile, consider lower-end plasmas for all but the brightest rooms.

Getting the best possible picture requires maximizing all of your viewing conditions, including ideal eye-to-screen distance for a given screen size, relatively central viewing angle, and as-low-as-possible ambient light. If you are willing to accommodate these criteria in your room, the best sets will deliver the best picture.

On the other hand, farther viewing distance, wider viewing angles and bright ambient room lighting are all factors that will decrease the quality of your TV, and cause the picture improvements produced by the best and most expensive HDTVs to be obscured.

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