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How to choose a video or
The most important specifications
measures the amount of detail that can be seen in an image.
For computers, resolution is expressed in the number of pixels
down and across the screen, and it's important that your projector
is capable of matching the resolution of your computer system.
VGA requires 640 x 480 resolution, S-VGA 800 x 600, XGA 1024
x 768. Standard 13" Macintosh monitors use 640 x 480
resolution, but to show a 17" Mac monitor full-screen
requires 832 x 624. Engineering workstations can require even
higher resolutions. For this reason, the resolutions of three-tube
projection systems are normally expressed in scan rate ranges,
to allow you to match them to the workstation or specialized
graphics card you may use.
video, resolution is expressed as the number of lines
per inch visible on a test pattern. The video resolution specification
(which is not the same as the horizontal computer resolution—and
actually is determined more by the electronics of the projector
than by the LCD panel) can serve as an overall indication
of the video quality you can expect.
As you start to compare LCD projectors, you'll need to know
the brightness in ANSI lumens (the current ratings standard,
and, please note, not comparable to "lumens" expressed
in non-ANSI terms). As a rough guide, a rating of 600 - 800
ANSI lumens works well with a 100" to 150" diagonal
screen with lights dimmed, but you'll want at least 1,000
ANSI lumens when you go to larger screens and 1,500 or more
if you want to project in bright lighting conditions. Your
best bet, of course, is to ask your sales rep to demo the
LCD projector under conditions typical to what you'll see.
and weight. There's often a trade off between small size
and image quality. If you depend on a sales force to voluntarily
take your projector and program from call to call, you may
find an ultra-compact LCD is your best bet, as an expensive
multimedia production does no good sitting in a closet or
a car trunk. Others may find, however, that a 12 to 15 pound
LCD projector offers a better combination of brightness and
price, yet is still very portable. Naturally, if you're going
to put the projector on a cart or a ceiling mount, size is
much less important.
video source. Do you need to show S-video or just standard
composite video? Will you take the unit overseas (and thus
need the ability to accept PAL or SECAM signals and overseas
power)? What's the resolution of the video? Projectors that
produce higher video resolutions produce sharper, cleaner
digital video systems are here, and many projectors now
include component video inputs to allow direct connection
to DVD players, plus digital TV tuners and VCRs when they
are available. It's important to note that any projector,
monitor or TV will be able to display digital TV signals.
If you want to take advantage of the HDTV clarity, however,
you'll need a higher-resolution video or computer projector,
and a component input will help by reducing noise. (It works
by dividing the chrominance portion of the video into red,
green and blue segments.) For more information about digital
TV, see our
digital television tech tips.
ratio is becoming important with digital TV formats as
well, and it's important that your projector will display
the aspect ratio of your source. Most computer and video images
use a 4:3 ratio—that is, the ratio of the width of the image
to its height is 4:3. But wide screen movies and HDTV formats
use 16:9 and SXGA, while it will display on a 4:3 monitor,
actually uses a 5:4 ratio.
type. Most LCD projectors use a metal halide or UHP source,
which offer a very white light and a useful life of 750 -
2,000 hours (depending on your projector model). They typically
do not burn out suddenly, but gradually grow dimmer, giving
you plenty of warning that it's time for a replacement.
ratio, which measures the difference between the brightest
white and darkest black your projector can produce, should
be an important spec, but there seems to be a problem in how
it's measured. We've done side by side comparisons between
LCD projectors rated at 100:1 and 300:1 and found little or
no difference in their images. We're now including contrast
ratio in our catalog, but it's a good idea to take this spec
with a grain of salt.
number of colors you need, while once important, is no
longer an issue. All of the LCD and other projectors United
handles offer 16.7 million colors.
Beyond the basics, you'll want to consider whether your LCD or
data projector includes:
resizing technology (also called "intelligent compression"
and other names), maps high resolution computer images to
a lower resolution LCD. This process works much better than
plain "compression," showing the entire image at
very acceptable sharpness. It works best going only one step
up. Using an 800 x 600 projector you'll get very good 1024
x 768 images, but 1280 x 1024 will be noticeably fuzzy.
digital video input (when used with a computer with a
digital video output), will increase the quality of your projected
image by eliminating the need to convert a digital RGB signal
to the analog RGB accepted by most projectors and monitors.
line doubler (or scan doubler) increases the number of
lines of vertical resolution from the 525-line standard to
1,050 lines. It does so by repeating each scan line, resulting
in a sharper-looking picture. It's important to note that
line doubling does not affect a projector's resolution spec,
since resolution is usually specified in horizontal
lens. Useful if you can't control the exact placement
of the projector.
correction or lens shift corrects rectangular distortion
caused positioning the projector away from the center axis
of the screen. Adjustable keystone correction is a real plus,
though nearly all projectors have at least a fixed correction
factor which allows you to position it below the center of
focus. Allows you to walk up to the screen and focus using
the remote control (for best accuracy).
control: operates your computer mouse from a wireless
remote control. If your PC has a USB mouse connector,
it will recognize a USB compatible mouse even if you
plug it in after you've started up your computer.
pointer also operates from the remote control. Laser versions
are the easiest to see (and to use).
loopthrough allows you to see your computer screen while
the image is being projected.
inputs allow you to switch between more than one computer
or video source.
amplifier and speakers. Most projectors have a sound system,
but the quality can vary (and the specifications you need
to judge that quality are not normally available). Still,
it's easy (and economical) enough to add a lightweight sound
system for use with large groups, and if you do so, you'll
have sound quality way beyond anything built into any projector.
Beyond the specifications
There are some comparisons that are very difficult to make from
a spec sheet (and, at times, the measurements that specifications
are based on aren't always made the same way). You'll really need
to see the projector or panel demonstrated to form a judgment,
accuracy. Besides the number of colors, how well does
the the unit handle subtle color renditions, such as flesh
tones? How clean are photos or video?
illumination. Does the image have hot spots or a clean,
even brightness from corner to corner? Is the focus consistent
from center to corner?
it's an 1024 x 768 projector, how good are the 800 x 600
and video images? Do any resolution trade-offs work for you?
Will the projector work through a critical presentation? Does
its manufacturer have a good reputation? Does it use a long-life
lamp? What's the warranty? Is it UL listed?
How long will you have to do without your projector if it
breaks? Will your dealer stand behind you if you need it for
a critical meeting?