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Given that light shines through an LCD panel, LCD projectors are a natural fit for front projection. LCD projectors are light and very inexpensive compared to CRTs, but lack the image quality. LCD projectors are so light that almost all portable projectors use LCD (Figure 19-27).

Figure 19-26 CRT projector

Figure 19-27 LCD projector (photo courtesy of ViewSonic)

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NOTE Another type of technology that’s seen in projectors but is outside the scope of the CompTIA A+ exams is called digital light processing (DLP). Check out the “Beyond A+” section of this chapter for details.

All projectors share the same issues as their equivalent technology monitors. LCD projectors have a specific native resolution, for example. In addition, you need to understand three concepts specific to projectors: lumens, throw, and lamps.

Lumens

The brightness of a projector is measured in lumens. A lumen is the amount of light given off by a light source from a certain angle that is perceived by the human eye. The greater the lumen rating of a projector, the brighter the projector will be. The best lumen rating depends on the size of the room and the amount of light in the room. There’s no single answer for “the right lumen rating” for a projector, but use this as a rough guide. If you use a projector in a small, darkened room, 1000 to 1500 lumens will work well. If you use a projector in a mid-sized room with typical lighting, you’ll need at least 2000 lumens. Projectors for large rooms have ratings over 10,000 lumens and are very expensive.

Throw

A projector’s throw is the size of the image at a certain distance from the screen. All projectors have a recommended minimum and maximum throw distance that you need to take into consideration. A typical throw would be expressed as follows. A projector with a 16:9 image-aspect ratio needs to be 11 to 12 feet away from the projection surface to create a 100-inch diagonal screen. A long throw lens has about a 1:2 ratio of screen size to distance, so to display a 4-foot screen, you’d have to put the projector 8 feet away. Some short throw lenses drop that ratio down as low as 1:1!

Lamps

The bane of every projector is the lamp. Lamps work hard in your projector, as they must generate a tremendous amount of light. As a result, they generate quite a bit of heat, and all projectors come with a fan to keep the lamp from overheating. When you turn off a projector, the fan continues to run until the lamp is fully cooled. Lamps are also expensive, usually in the range of a few hundred dollars (US), which comes as a nasty shock to someone who’s not prepared for that price when the lamp dies!

Common Features

CRT or LCD, all monitors share a number of characteristics that you need to know for purchase, installation, maintenance, and troubleshooting.

Size

You need to take care when buying CRT monitors. CRT monitors come in a large number of sizes, all measured in inches (although most metric countries provide the metric equivalent value). All monitors provide two numbers: the monitor size and the actual size of the screen. The monitor size measures from two opposite diagonal corners. The actual screen is measured from one edge of the screen to the opposite diagonal side. This latter measurement is often referred to as the viewable image size (VIS). You will commonly see a size difference of one to two inches between the two measurements (see Figure 19-28). A 17-inch CRT monitor, for example, might have a 15.5-inch VIS.

Figure 19-28 Viewable image size of a CRT

LCD monitors dispense with the two values and simply express the VIS value. You must consider this issue when comparing LCDs to CRTs. A 15-inch LCD monitor will have about the same viewing area as a 17-inch CRT.

Connections

CRT monitors for PCs all use the famous 15-pin, three-row, DB-type connector (see Figure 19-29) and a power plug. The DB connector is also called a D-shell or D-subminiature connector. Larger or multipurpose monitors may have a few other