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Education | Display Methods
The most popular video display options
LCD
Liquid-crystal displays (LCDs) are today’s most popular choice for flat-
panel video displays. These low-power, flat-panel displays consist of a
liquid containing crystals sandwiched between filtering layers of glass or
plastic. When electric current is passed through the material, the
molecules of
the liquid crystal twist so that they either reflect or transmit light from
an external source, usually a cold cathode fluorescent lamp (CCFL).
LED
LED displays are actually LCD TVs that use LEDs as their light source,
instead of traditional CCFLs. In fact, these displays are often referred to as
LED LCDs. LED displays tend to be brighter and perform better than LCDs,
but they also tend to be higher-end models, which may have more to do
with their superior performance than their technology.
Plasma
Plasma flat-panel displays use small cells that contain electrically charged
ionized gases, which fluoresce when electrically charged. Although
plasma displays are waning in popularity and are available only in larger
sizes
— generally 42 inches and up — their deep blacks and high contrast
ratios
make them a good choice when implementing large displays that are
intended to be eye-catching.
Professional grade vs. consumer grade
When selecting a video display, you may find that “professional
grade” or “commercial grade” models cost significantly more than
televisions you can buy at the local “mega mart.” The primary
difference is that professional-grade displays are built to stay on 24/7
for weeks and months at a time without breaking down. They may
also offer features such as video-wall processors, scheduling options,
and lockable control panels not normally found in consumer-grade
televisions.
Other video display options
CRT
Older cathode ray tube (CRT) displays are still around; usually they’re older
analog TVs or VGA monitors. They’re bulky, offer low resolutions, and look
very dated but can be a low-cost option in areas where appearance is
secondary.
Projected
A front or rear LCD/DLP projector is a compact device that projects an image
on a screen. These devices are handy for trade shows, meetings, or
anywhere it would be impractical to bring along a full-sized monitor.
OLED
Organic light-emitting diode (OLED) displays are the displays of the future.
They’re lightweight, thin, and energy-saving but not yet available at a price
that makes them practical for general use.
Video-wall specific displays
These can be LED video cubes or rear-projection cubes that are designed
to be stacked on one another for a virtually seamless video wall display.
Factors to consider when choosing a display
Picture quality
Plasma displays reproduce color more accurately with deeper blacks and
display moving images with remarkable clarity. They provide excellent
performance with their high-contrast levels and color saturation, and have
the edge when it comes to viewing angles. In fact, plasma screens have as
much as a 160° viewing angle, whereas LCDs display at 130 – 140° angles.
However, they also carry the risk of image burn-in (the permanent disfiguring
of a screen image caused by the continuous display of a high-contrast
object).
LCD displays, on the other hand, don’t have quite the color accuracy of
plasmas, but they’re brighter and have a sharpness advantage with a higher
number of pixels per square inch. These additional pixels make LCD
technology better at displaying static images from computers or VGA sources
in full-color detail. Applications with large amounts of data and written
material display particularly well on LCDs. What’s more, there’s no risk of
image burn-in.
Durability
With LCD screens, there are essentially no parts to wear out. They last as
long as their backlights do, with displays lasting, on average, 50,000 – 75,000
hours. That’s why LCD screens are especially good for applications such as
digital signage or displays that require around-the-clock use.
Plasma screens, however, use a combination of electric currents and noble
gases (argon, neon, and xenon) to produce a glow, which in turn yields
brilliant color. The half-life of these gases, however, is only around 25,000
hours. The glow they produce grows dimmer over time. They’re also prone
to burn-in or ghosting of images, although this is less of a problem with
newer models.
Power consumption
Early plasmas had a very high power consumption; some as high as 5W per
square inch. These values are now down in the 0.3 – 1.0-watt range,
depending on screen size. LCDs typically run in the 0.1 – 0.3-watt per square
inch range, and LEDs are even lower. Manufacturers are now required to
provide power consumption information, but keep in mind that there are two
values for consumption, default and calibrated, so be sure you’re comparing
like values.
Making the choice
In general, plasma produces a clearer picture with a wider viewing angle and
a better response time for fast motion playback, making it a good choice
whenever you need a large screen to show a very visually active display, for
instance, in applications displaying sports footage or active advertisements.
LCDs are better at displaying detailed, static information. Because LCDs are
brighter, they’re ideal for venues with lots of ambient light. They’re also the
best choice for 24/7 applications because of their lower power consumption.
For these reasons, LCDs are preferred for professional AV display installations.
Choosing the
right display