Buying the right HDTV is actually much harder than walking into a store and laying down some plastic - and certainly much harder than it should be. But there are quite a few things you can do to prepare yourself.
Virtually identical issues apply to buying computer monitors, so keep the following info and tips in mind the next time you're in the market for a monitor as well.
1. First, ALL manufacturer's published specifications are exaggerated by unknown factors - we discussed this in our previous HDTV display story - so you can't rely on them as part of your analysis. Within a particular manufacturer's own product line the specs will tell you a bit about the marketing pecking order for their own models, but DO NOT use specs to compare models from different manufacturers.
2. Do your homework. Read reviews from several websites and magazines, but note that there are only a handful of publications that do real objective testing and they can only test a small fraction of all of the available models (a few personal favourites include DisplayMate's analysis, Television Info and Sound and Vision).
3. Visit the manufacturers website and read all of the model information carefully. If a manual for the HDTV is available online, study it very carefully – in my opinion it's by far the best evaluation tool you have.
4. Quick recommendation – get a plasma for HDTV viewing in subdued ambient lighting and an LCD when there is bright ambient lighting.
5. Next, get thee to a retailer – but, when choosing a store, keep in mind: There are big box retailers like Best Buy and Walmart, medium box retailers like Target and Sears, and finally the small box Audio-Video specialty retailers. The bigger the store the more the "look but don't touch" attitude prevails.
Once You're in the Store
1. Most stores have their own continuously running demos, but they are designed to make everything look good – it's called "eye candy" for a reason. Generally the picture quality of the demos are not very good. What is especially important is that all of the HDTVs show exactly the same video content at the same time.
2. If they are showing animated videos, ignore them. They're artificial images and as such, you'll have no absolute reference to evaluate them with. The brightest and most colour saturated TV will appear to be the best in these circumstances, but isn't. The lack of an absolute reference also applies to movies such as Avatar (because the Navi are blue). It's a great movie, but not for the evaluation of picture quality and accuracy!
3. In-store HDTVs are almost always poorly and inconsistently adjusted, so you can't judge picture quality and colour accuracy based on what you see. Even in Best Buy's high-end Magnolia Home Theatres, the TVs are often inaccurately adjusted. A TV that doesn't look first-class may be a misadjusted great TV or a mediocre TV showing at its best. If the picture looks great that means it can likely do even better with your own adjustments or a professional calibration. It could also simply be the unit with the highest dealer profit margin.
4. Many retail stores still deliver video to the HDTVs using analogue distribution instead of digital because it's a lot cheaper. Analogue introduces a whole other layer of issues that further complicates displayed picture quality, so it's important to find out if the distribution is analogue or digital.
5. Something to keep in mind: ambient lighting is generally bright, irregular and awful. Fluorescents are the worst; the dark is best.
6. The HDTVs are often placed at different heights, which introduces viewing angle issues which particularly affect LCDs. When evaluating an LCD be sure to stand directly in front of the centre of the unit because of viewing angle issues (see below).
7. When TVs are displayed side by side, there is a natural tendency to believe that the brightest, most colourful TV with the highest image contrast is the best – a punchy picture that stands out from the crowd. A TV that is delivering an accurate picture will then appear bland. Most TVs come from the factory set to a vivid mode that exploits this psychological bias. Try to overcome that… because you won't want that sort of picture at home.
What you can do
1. Live video isn't good for evaluating picture quality because it's changing continuously. Still image slideshows work best. You can then compare several HDTVs at once; also change your viewing position to look for viewing angle issues, which can be plentiful with LCDs.
2. Small box retailers will often let you bring your own favourite DVDs and Blu-ray discs – big and medium box retailers typically will not. However, they're a great evaluation tool because you have a pretty good idea what the pictures should look like. Four of my favourites: Seabiscuit, because of the great facial close ups and indoor scenes; Dark City and Escape from New York, because they evaluate very dark picture quality; and Over America for the fast moving spectacular day and night scenes. Make a list of the chapters that you want to look at.
3. Even better, bring a USB Thumb Drive with you loaded with evaluation photos; many HDTVs now have USB inputs and in many cases the store will allow you to use them. Include both challenging high quality professional photos and also family photos – they are the best absolute reference you have because you know exactly what everyone and everything is supposed to look like.
4. Talk to a sales person and see if they will let you play with the remote control. If they do, set the TV to a Cinema mode and explore the menus.
5. If you're adept enough, tweak the adjustment controls while looking at the content you've brought along to see if you can get better and more accurate colours and picture quality.
What to look for
1. Check the screen for reflections and avoid glossy screens unless you will be watching in the dark. Many glossy screens introduce ripples in the image because they are glued on poorly. The best time to check for screen reflections is when the screen is black – then look for ripples in the screen reflections as you shift your viewing position slightly. Most store demos will go to black at least once. If you brought along a USB Thumb Drive, include a totally black picture by taking a photo with the lens cap on.
2. Obviously the best time to check the black level brightness is when the screen goes black – but this may be difficult to determine in a brightly lit store. Also check for screen non-uniformities, dead pixels and backlight leakage around the edges of the screen.
3. The picture on most HDTVs will change with viewing angle, this is particularly true with LCDs but the effect should be minor in plasmas. You'll need a still photo to evaluate the change with both horizontal and vertical viewing angle. Peak brightness, black brightness, contrast ratio, image contrast and colour (both hue and saturation) will change with viewing angle. Use a nice colourful photo that includes a wide range of colours and intensities with a large face plus a number of well known objects for reference.
4. LCDs with IPS (In Plane Switching) technology will not show a strong colour shift with angle changes like the other LCD technologies, but will show a large shift in black brightness which can have a considerable effect when viewing dark scenes. So watch the black photo or a dark scene from a broad and varied viewing angle.
5. LCDs all have trouble at the very bright and very dark ends of the intensity scale. Unfortunately, manufacturers often try to squeeze extra brightness out of every HDTV despite the fact that they are already plenty bright for most applications. They wind up overdriving the display into what is called white saturation or clipping – it makes the picture look like an overexposed photo with highlights somewhat washed out in colour and contrast. Photos with very bright highlights are best for evaluating this (unless you have some special DisplayMate test patterns). If the highlights look washed out, turn down the Contrast Control. If that doesn't fix it, pass on that model.
6. One last thing to bear in mind: most HDTVs make noise – typically a power supply whine and fan noise. That's going to be very hard to evaluate in a noisy store, so get real close to the unit and put your ear right up to it and listen.
Dr Raymond Soneira is President of DisplayMate Technologies Corporation of Amherst, New Hampshire, which produces video calibration, evaluation and diagnostic products for consumers, technicians and manufacturers. See www.displaymate.com. He is a research scientist with a career that spans physics, computer science and television system design. Dr Soneira obtained his PhD in Theoretical Physics from Princeton University, spent five years as a Long-Term Member of the world famous Institute for Advanced Study in Princeton, another five years as a Principal Investigator in the Computer Systems Research Laboratory at AT&T Bell Laboratories, and has also designed, tested and installed colour television broadcast equipment for the CBS Television Network Engineering and Development Department. He has authored over 35 research articles in scientific journals in physics and computer science, including Scientific American. If you have any comments or questions about the article, you can contact him at [email protected]
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