Black Box AVSP-DVI1X8 Dokumentacja Pobierz pdf (Strona 16)

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Education | AV Distribution Tutorial

Version April 2013

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

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