Screen Resolution and Aspect Ratio
Many people are familiar with the concept of screen resolution.
Resolution is a measurement of how many individual pixels your
TV
or computer monitor can display at once. The old cathode ray TV (CRT)
in your basement can display the equivalent of about 300,000 pixels
[source:
Kindig]. The latest
HDTVs
can display more than 2 million pixels. With more pixels, the image can
be rendered in greater detail. It's the difference between painting a
portrait with a thick sponge block or a small, delicate brush.
The
standard way to classify TV resolution is with numbers like 480i, 720p,
1080i and 1080p. The bigger the number, the greater the screen
resolution. The little "i" and "p" stand for
interlaced and
progressive scan. This has to do with the way in which the image is rendered on the screen. Refresh rates on TVs and
computer monitors
are measured in hertz. A refresh rate of 60 times per second translates
to 60 hertz. An interlaced-scan TV refreshes half of the screen image
60 times per second. It refreshes the odd-numbered horizontal lines
first and then the even-numbered lines. The result is that the full
screen refreshes 30 times a second.
On a progressive scan
television, the entire screen refreshes 60 times a second. The result is
that progressive scan TVs have a noticeably smoother image when
watching sports or other video with fast-moving action. All computer
monitors are progressive scan [source:
PCMag.com].
Some even have refresh rates faster than 60 times a second. This is why
interlaced SDTVs make for lousy computer monitors. When you scroll, the
image can't refresh fast enough to keep things smooth. As a result, you
see that telltale flicker.
Resolution is important, but you must
also take a screen's aspect ratio into account. Your goal when hooking
your TV up as a monitor is to make the entire image fit within the
boundaries of the TV screen. SDTVs use a 4:3 aspect ratio -- the ratio
of the screen's width to its height is 4 to 3. HDTVs have a native 16:9
aspect ratio. While many computer monitors share those aspect ratios,
not all of them do, and your computer may support many different screen
resolutions with different aspect ratios.
In fact, your computer's
preferences are unlikely to tell you the aspect ratio, and instead will
tell you the resolution. The horizontal x vertical measurement is also
the most common way to label computer monitor resolution. Some typical
monitor resolutions are 640 x 480, 800 x 600 and 1024 x 768. If you
don't know your monitor resolution, you can find out by going to
whatismyscreenresolution.com.
If you aren't connected to the Internet and you're using a Windows PC,
right-click on the desktop and choose Preferences. Then choose the
Settings tab. On a Mac, go to System Preferences and click Displays.
The
trick is to find the resolution that best fits the TV's aspect ratio.
This may not be as big a deal as it sounds, though. Modern operating
systems can usually match the attached monitor's aspect ratio
automatically. If your computer doesn't, you can manually adjust the
settings in your computer's preferences to make it fit.
But
there's more to hooking these two machines together than resolution and
aspect ratio. You still have to get the information from the computer to
the TV. In order to do that, we've got to solve the cable conundrum.
Computer TV Cables
If you read our article "
How do I know which cables to use?"
then you know there is a baffling number of audio/video cables on the
market. You'll have to make some sense of the different types of wiring
necessary to connect your computer to your TV. First you need to figure
out what kinds of audio/video outputs your computer has and what kinds
of audio/video inputs your TV has. If you're lucky, you'll find a match
right away. But depending on the type of equipment you own, you may need
to get creative.
First, let's talk about which cables you'd use
to connect a computer to a standard-definition TV. The most common video
inputs on an SDTV are composite, S-video and component video. On
computers, the most common video output is S-video. On a desktop PC,
you'll find the 9-pin S-video jack on your graphics card next to where
you connect your monitor.
Some Windows laptops also have
S-video-out jacks, but most have 15-pin VGA jacks for connecting to
external monitors. Luckily, it's easy to find adapters and special
cables that have VGA connectors on one end and S-video connectors on the
other. Apple also sells a wide variety of adapters to connect Mac
desktops and laptops to the S-video or composite jack on SDTVs.
Even
if you have an old TV that only accepts coaxial video cable (the
one-pin variety that's mostly used for cable TV and satellite
connections), you can use something called an
RF converter box that can convert S-video or VGA input into coaxial output.
For
connecting a computer to an HDTV, it's the same story. The most common
HDTV inputs are component video, DVI and HDMI. If your graphics card
doesn't have one of these outputs, then you'll need to buy a special
converter box or adapter. For example, if your computer only has a VGA
jack and your HDTV only accepts HDMI, then you'll need to buy a small
box that will convert the signal for you.
If you're serious about
playing high-definition content from your computer on your HDTV, then
you should upgrade to a graphics card with a DVI or HDMI output. Most
newer Apple laptops come with a Mini DisplayPort video output that
easily connects with the DVI or HDMI inputs on an HDTV.
All of the
cables that we've mentioned so far are video-only cables, which means
that you'll need separate cables to handle your audio. The easiest
solution is to connect some computer speakers to your audio card's
headphone or audio-out jack. If you want to use your TV's built-in
speakers, then you'll need to buy a 1/8-inch stereo mini-plug-to-RCA
cable.
For the best possible audio, you'll need to invest in an
audio card for your computer with either an optical or digital coaxial
audio output. These connections carry high-bandwidth digital audio
signals using cables that can be plugged directly into your home theater
receiver.
Even if you have the right cables and have done your
homework about resolutions, you still might have some problems
connecting your computer to your TV. In the next section, we'll share
some troubleshooting tips.
Computer to TV Troubleshooting
The biggest problem with connecting your computer to your
TV
is that, generally speaking, computers and TVs don't display at the
same resolutions. For example, the closest thing to the HDTV resolution
720p (1280 x 720) is a monitor display mode called XGA (1280 x 960). Not
quite the same. And the closest thing to 1080p (1920 x 1080) is a
monitor display mode called WUXGA (1920 x 1200). Again, not quite the
same.
The result, in most cases, is something called
overscan,
where the full computer screen image doesn't fit on the TV screen.
Overscan is a bigger problem on SDTVs where the native screen resolution
is much smaller than your computer's display. If you're going to use an
SDTV as a monitor, plan on lowering your screen resolution to 800 x
600.
HDTVs
also have overscan problems, but usually only the very edge of the
computer image gets cropped. A bigger problem with HDTVs is when the TV
refuses to display a signal that doesn't fit its native resolution.
Luckily, most HDTVs have the ability to
scale incoming signals to match their native screen resolution. This involves either
upconverting lower-resolution signals in the attempt to bring the resolution up to high definition or
downconverting
higher-resolution signals for lower-resolution screens. It's not
perfect, but for most casual viewers, there's little to no noticeable
loss in image quality.
In rare cases, the HDTV won't recognize the
resolution of the signal sent by your computer. When you connect an
external display to your computer, most
graphics cards
will automatically try to find a good match for the display's native
resolution. If this doesn't work, you will probably need to edit your
resolution with third-party software.
Two programs are considered
the best solutions for solving connectivity problems between a computer
and a TV: PowerStrip for Windows and DisplayConfigX for Mac. Both of
these programs allow you to match your graphics card's resolution
precisely with the native resolution of your TV. If your HDTV is 1080p,
you can go into one of these programs and switch your computer's
resolution to 1920 x 1080, even if this wasn't previously an option.
Avoid
increasing the refresh rate on your graphics card, unless you have a
120-hertz HDTV. If you send a signal with a refresh rate over 60 hertz
to a normal HDTV, you could damage the TV [source:
Komando].
