 January 1, 2005
Display Pluses and Minuses
There was a day when a TV set was
simply a TV set. It used a cathode-ray picture tube, took up lots of room, and generated
lots of heat. That technology is now more than 70 years old, so it’s not surprising
that it’s been joined by more advanced display types, although there are certainly
still lots of CRTs around.
Over the next few months, I’ll have a look at each of
these new technologies in turn. For now, however, it seems useful to provide a brief
rundown of the advantages and disadvantages of the various types, which you can check when
we get to the individual displays. The information is based on the analog NTSC standard
mostly used in North America today, but the new display formats will all be available in
digital form, and the comparisons will be equivalent.
Direct-View CRT (cathode-ray tube)
Technology: Decades-old technology, but still offers
the most performance per dollar.
Picture quality: At its best, superb.
Brightness: Good. In fact, most sets are adjusted to be too bright.
Viewing angle: Very good, especially with new flat tubes.
Color rendition: Excellent, if properly set up.
Setup: Dead simple if you just want to plug it into the cable. Can be tricky if you
want to use all the bells and whistles.
Best use: Home viewing, where seats are relatively close to the screen.
Cost: Wide range. Can be very economical.
Future: Will remain the standard technology for the foreseeable future.
Rear-Projection CRT
Technology: An adaptation of regular CRT technology,
using extra-bright tubes focused on the screen from behind.
Picture quality: Can be excellent. Some sets have difficulty reproducing a true
black.
Brightness: Good, especially in a room with dim lighting.
Viewing angle: Varies considerably. Some models have a pronounced "hot
spot" visible when watching on axis, and a notable falloff of brightness to the
sides. Others are admirably consistent, as long as the viewing angle isn’t too
extreme.
Color rendition: The best sets are now very close to equivalent direct-view sets.
Setup: About as easy as a normal TV. Its bulk may make it more difficult to
position.
Best use: Home-theater systems, especially in larger rooms or where a fairly large
image is wanted.
Cost: Equivalent to direct-view sets on a dollars-per-inch basis.
Future: Remains the big-screen standard for now, but will probably lose out to
newer technologies as their prices come down.
Front-Projection CRT
Technology: Shares a lot with rear-projection CRTs,
but the tubes are in a separate module and are focused on a separate screen.
Picture quality: Usually excellent.
Brightness: Normally fairly dark, mainly because the image is usually projected
onto a larger screen than other formats. Brightness is helped by using curved,
high-reflectivity screens.
Viewing angle: Wide when flat screen is used, narrower with curved screen.
Color rendition: Can be excellent.
Setup: Very finicky. Proper installation should be done by a professional for best
results. Positioning should be permanent.
Best use: Boardrooms and other demonstration areas. Other than size, offers little
advantage over other systems.
Cost: High.
Future: Will probably soon be eclipsed by other technologies, especially DLP.
Direct-view LCD (liquid-crystal display)
Technology: Screen is made up of thousands of
individual pixels that pass or block light from a light source behind.
Picture quality: Depends on number of pixels used. Early models were quite coarse,
but recent models, especially larger ones, can produce very good pictures.
Brightness: Can be good when viewed on axis. Tends to drop sharply when viewed from
an angle.
Viewing angle: Often quite narrow. Because the pixels become opaque, they also
become reflective, which means ambient light can wash out the image when it is viewed from
an angle.
Color rendition: Usually good.
Setup: Thinness and lightness a big advantage. No big operating problems.
Best use: Small-screen and portable applications, as well as laptop computers.
Cost: Moderate.
Future: Will continue to be the standard where portability and convenience are more
important than the highest picture quality.
Front-projection LCD
Technology: Uses an LCD panel like a moving
transparency, projecting light from an external source through a lens onto a separate
screen.
Picture quality: Early models were coarse compared to other systems; more recent
projectors are excellent.
Brightness: Good, especially if three LCD panels are used, one for each primary
color.
Viewing angle: Wide.
Color rendition: Good.
Setup: An LCD projector’s single lens makes it a snap to set up, focus, and
zoom.
Best use: Applications in temporary locations and where a large image is required.
Cost: Moderate.
Future: Will continue to be the workhorse for sales presentations and the like, but
will undoubtedly lose out in the end to something like DLP.
Plasma
Technology: As in an LCD display, the screen
is divided into individual pixels, but each is a controllable light source.
Picture quality: Depends on number of pixels used. Most plasmas are now made with a
view to digital television and so are capable of very sharp images.
Brightness: Good now; the first examples tended to be somewhat dim.
Viewing angle: Wide.
Color rendition: Early models were only just acceptable; today’s are much
better.
Setup: Easy to operate, and there’s nothing to set up. Thinness is an
advantage, but weight might be a problem in some applications.
Best use: Home theaters in which a fairly large screen is wanted but space is at a
premium.
Cost: High.
Future: Might well replace CRT as the prime direct-view system when quality goes up
a notch and prices come down several notches.
DLP (digital light processor)
Technology: Each picture element, or pixel, contains
a microscopic mirror that can be tilted to reflect or not reflect light from an external
source. Projects the image through a single lens, much as an LCD projector does. Rear- and
front-projection models available.
Picture quality: Depends on number of pixels. Virtually all DLPs have enough for
superb images. Like LCD, best if three panels are used.
Brightness: Extremely high, if necessary. Professional units are brighter than
movie projectors.
Viewing angle: Wide.
Color rendition: Excellent.
Setup: Equivalent to LCD front projectors.
Best use: For now, commercial applications where very large screens and bright
images are required.
Cost: Equivalent to LCD.
Future: Might well become the standard projection system. May be used in commercial
movie theaters, replacing film projectors.
...Ian G. Masters
igmasters@soundstageav.com
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