The Specs
Buying an HDTV requires more than just
deciding how big a screen you want, looking
at some sets, and purchasing the one with
the best picture (you guess) that fits your
budget. An options explosion has littered
the shopping landscape with numbers,
features, and terminology that even experts
sometimes have trouble tracking. When
you're finding your way in the high-def, A/V
world, don't just go for the gaudiest
numbers--some are important, sure, but
others aren't. Let's quickly walk through a
few.
Important: Contrast Ratio
Contrast ratio refers to the brightest
and darkest light values a display can
produce at the same time. All else being
equal, the higher the contrast ratio is, the
better the quality is. All else is seldom
equal, however.
Pumping up the maximum light output, for
example, will increase contrast, but it
won't do anything to help pitiful black
levels--that, in our opinion, is a much
greater concern. LCDs in particular have a
tougher time dealing with darks. So take
contrast ratings as a very rough guide to be
supplemented by eyes-on evaluation. LCD
contrast-ratio specs start at about 600:1,
while those for plasmas start at about
1000:1. Although ratings of 10,000:1 or
better are becoming common for both types of
displays, you should approach such claims
with a healthy bit of skepticism.
Since no true standard method for
measuring contrast ratio exists,
manufacturer exaggeration is rampant.
Independent reviews are a more reliable
guide, but in the end you need to trust your
own eyes. Keep in mind that when you're on a
showroom floor, you're checking out the
HDTVs under the store's lighting conditions,
not yours. Will you watch in a dark cave or
in a well-lit, open space? Probably the
smartest idea is to check the store's return
policy before buying.
Important: Aspect Ratio
The aspect ratio describes the
relationship of screen width to screen
height. Conventional sets have a 4:3
aspect ratio, whereas wide-screen models
are 16:9. Wide screens are the
future. For one thing, HDTV is a wide-screen
format. For another, DVDs usually look
better on wide-screen displays because
nearly every movie made in the last 50 years
was filmed in an aspect ratio of either
1.85:1 (very close to 16:9, which is 1.78:1)
or 2.35:1 (even wider than 16:9).
Important: Video Inputs
The number and type of video inputs
determine which sources you can use with the
display.
Composite video: This
input type has the lowest quality but the
broadest compatibility. Any device that has
video outputs will include composite video
among them. Connection is made with a single
75-ohm coaxial cable between RCA jacks.
S-Video: S-Video offers
better quality than composite video does,
and most video sources except standard VCRs
now have S-Video outputs. Connection is made
with a special cable and multipin sockets.
Component video: This
high-quality option is the minimum standard
for connecting high-definition cable and
satellite set-top boxes, as well as
progressive-scan DVD and Blu-ray Disc
players. It requires three 75-ohm coaxial
cables of the same type used for composite
video.
VGA (Video Graphics Array):
This high-quality analog RGB connection is
used primarily for computer connections.
DVI (Digital Video Interface):
One of the highest-quality types of inputs.
This digital video connection can attach to
devices with HDMI outputs (see below) by
means of an adapter. It may also be used for
computer connections. Requires a special
cable and multipin sockets. Some displays
with a DVI input may work only with
computers, so watch out for that if you plan
to connect an HDTV source, such as an HD
digital cable box or a Blu-ray Disc or HD
DVD player. Another thing you need for
guaranteed HDTV compatibility is compliance
with the HDCP (High-bandwidth Digital
Content Protection) system.
HDMI (High-Definition Multimedia
Interface): Also of the highest
quality, HDMI is DVI plus a digital audio
and control link. HDMI is the dominant
digital connection interface for HDTVs
today. The big draw here is that you get a
one-wire setup that pumps HD content into
your other home-theater components too. This
connection is provided on almost all current
HD satellite receivers, HD cable boxes, and
upconverting DVD players (those that provide
720p, 1080i, or 1080p output from regular
DVDs), and it is the standard video
connector for Blu-ray Disc players. The
exact version of the HDMI input (for
example, 1.1 or 1.3) is of little
consequence on TV sets currently on the
market. Of more importance to HDTV shoppers
is how many HDMI inputs a TV has. Aim to get
an HDTV with at least three or four HDMI
inputs, to accommodate the multiple devices
you're bound to accumulate.
HDMI CEC: HDMI inputs may include support for the
Consumer Electronics Control (CEC) protocol, which enables CEC-certified
components to send control information back and forth to one another.
This arrangement can allow single-remote--or even single-button--control
of functions involving multiple components, such as a TV, DVD player,
and A/V receiver. Manufacturers tend to have their own names for HDMI
CEC, such as CE-Link (Toshiba) and Anynet (Samsung). In many cases the
CEC functionality is restricted to components from the same maker, which
obviously lessens the benefit in a mixed-brand system.
Important: Resolution
Non-CRT displays, such as plasmas and LCDs, are fixed-pixel arrays,
meaning they have rows and columns of individual picture elements that
turn on and off to produce the necessary patterns of light. Resolution
is specified as the number of pixel columns by the number of pixel
rows--640 by 480, for example, or 1280 by 720. Resolution and contrast
ratio determine perceived picture detail.
Digital content currently is delivered in one of five formats: 480i,
480p, 720p, 1080i, and 1080p. The 480i format is the same as that used
for standard analog TV, and when programming originally in 480i is
delivered by digital cable or satellite to your home, it retains that
format. DVDs are sometimes mastered in 480p, but mostly they are 480i; a
progressive-scan DVD player can de-interlace 480i DVDs to create 480p
output, however. The 720p and 1080i formats are used by satellite,
cable, and over-the-air-broadcast high-definition content providers, as
well as some advanced DVD players that upconvert 480i and 480p content.
Blu-ray Discs output 1080p video, though Blu-ray players can deliver the
content in 1080i or 720p format for displays that do not accept 1080p
input.
Given that the price differential between 720p and and 1080p has
narrowed considerably, we recommend buying a set that supports 1080p.
Your new HDTV represents a long-term investment. Some online streaming
services, such as Vudu and Dish Networks' on-demand options, are
offering 1080p today, and we expect more services to follow in the
future. If your budget can handle 1080p, go for it.
Generally speaking, a
display is considered high-definition if it is wide-screen and has a
total pixel count approaching 1 million. So 1920 by 1080 (1080p), 1280
by 720 (720p), 1366 by 768, 1024 by 1024, and 1024 by 768 are all
examples of high-definition display resolutions. The larger the screen
and the closer you sit to it, the more important its resolution becomes.
|
Somewhat Important:
Screen Size
Size matters, don't get us wrong. But just because you can afford a
65-inch monster, that doesn't mean you should buy one. You need to
factor in the screen size and where you plan to watch the TV. Having
your nose pressed up against the display in a broom closet of a room is
hardly "ideal viewing conditions."
To determine the best viewing distance, and therefore how much space
you'll need in your TV room, remember this simple bit of math: Note the
screen size in inches and multiply it by 2. Calculators ready? Take, for
example, a 52-inch set. The sweet spot for viewing is 104 inches away,
or a little more than 8.5 feet from the screen (8.66666667 feet if you
want to be nitpicky about it). You don't have to be exactly on target;
simply bear this in mind as you plan where to place your new set.
Somewhat Important: Built-In Tuners
Most current flat-panel displays include a tuner for conventional
analog broadcast and cable-TV reception and for broadcast HDTV. A few,
however, are strictly business--they're monitors with no built-in tuner
(more common for plasmas than for LCDs). That may not matter if you
receive all your TV programming via satellite or cable, but if you want
to watch broadcast TV over an antenna, be sure that the set you buy
includes a TV tuner. Most sets also have built-in tuners for digital
cable TV (referred to as ATSC digital tuners). Although such tuners have
a standard for handling scrambled premium channels (for example, HBO),
many sets do not support it, so be sure you know exactly what you are
getting. If you're interested in that capability, you may know about
CableCard (a few sets in the recent past offered a CableCard slot). But
CableCard is giving way to the new Tru2way standard, which can banish
the external box if both your TV and your cable provider support it.
Somewhat Important: Refresh Rate
Refresh rate refers to the number of times per second a new image
displays on the screen. The standard refresh rate for television in
North America is 60 times per second, or 60 Hz (hertz), and until fairly
recently that was it. Now, however, many high-end LCD HDTVs offer a
120-Hz refresh rate. Usually the TV set achieves the higher rate by
interpolating new frames between the ones that are broadcast. The tactic
helps minimize or eliminate the blurring of fast motion that sometimes
occurs on LCDs because of their relatively slow response times (how long
they take to switch between black and white or between dark gray and
light gray).
Done well, 120-Hz refresh can be very effective; but done poorly,
motion can appear slightly unnatural. As always, look at a set and judge
its performance before you buy. Also find out whether the 120-Hz
processing is switchable, so that you can turn it off if you don't like
it or you don't need it. As response times and video processing of LCDs
improve, the need for refresh-multiplication is diminishing.
Because plasma sets have very fast response times, they don't require
120-Hz processing (though it may start showing up in them simply for
marketing reasons). A nonstandard refresh rate presents another
potential benefit, however, when you're viewing material that originated
as film. Movie film is shot at 24 frames per second and displays in
theaters at 48 Hz, with each frame flashed on the screen twice. But
putting movies on TV at the standard refresh rate is a little tricky,
since 24 does not divide evenly into 60. The conventional solution is to
stagger the frame repetitions, displaying the first frame twice, the
second three times, the third twice, and so on. Although such 2:3 (or
3:2) processing works pretty well, it imparts a subtle stutter to
on-screen motion.
Typically, viewers are so accustomed to this artifact that it seldom
jumps out; but once you notice the effect, it's as plain and obvious as
can be. The TV can eliminate it, yielding a slightly smoother
impression, if the set has the ability to switch to a refresh rate
that's an even multiple of 24 Hz for film-based content. Pioneer
plasmas, for example, run at 72 Hz for film material, and the 24-fps
output options of some Blu-ray Disc players are designed to facilitate
the same sort of processing. Since 120 Hz is an integral multiple of 24
Hz, the opportunity exists to do something similar in high-refresh-rate
LCDs, depending on how the display's interpolation processing is
designed.
Minor: 24p Input
Some Blu-ray Disc players can provide 24-fps 1080p video from their
HDMI outputs for discs mastered at 24 fps, matching the frame rate of
the film original. If the TV connected to such a player can accept
24-fps 1080p (24p) video and can operate at a refresh rate that is an
integral multiple of 24 Hz (such as 72 or 120 Hz), it can process the
video to create slightly smoother motion than if it were to convert the
footage to the standard 60-Hz refresh rate. The benefit is relatively
subtle, however, and not very many TVs offer such processing yet; even
some sets that accept 24-fps signals just convert them to 60 fps for
display. Be sure you know what you're buying.
Minor: Ethernet Port
Some HDTVs now provide ethernet ports, which can give you access to
the Internet or to content (such as pictures) streamed over a home
network. Features available via ethernet vary somewhat from manufacturer
to manufacturer, so confirm what you're getting before you lay out the
cash. (This is a feature that new operating systems like
Microsoft Windows 7 will utilize)
Minor: USB Port
Some HDTVs now have USB ports. Usually they are intended for
connecting to flash drives containing pictures, music files, or possibly
updates to the TV's internal operating software (firmware). The exact
functions of USB ports vary somewhat from one TV to the next, so do some
research prior to committing to a set.
Minor: Comb Filter Type
Comb filters are necessary in analog TV to separate color and
luminance information without losing too much detail, but that's not an
issue in HDTV. The only time the comb filter comes into play is for
analog TV reception or any signal coming in via a composite-video
connection. For all other connections, it's out of the loop. In any
case, the comb filters in flat-panel TV sets are routinely very good
these days.
The above specification explanation is from PC World.
 |
