Chapter 16: Monitors and Displays^371
The front glass panel on a standard CRT is like a section out of a ball—curved both
horizontally and vertically. This places each phosphor element the same distance from
theelectronbeams,whicheliminatesthedistortionalongtheedgesofthedisplaythatcan
be common in flat-screen CRT displays. The electrons on a flat-screen display have
further to travel. As a result, they are less focused and arrive slightly later than those in
the middle portion of the screen, making them appear slightly distorted.
Some displays, such as the Sony Trinitron CRT, compromise with a CRT that is like a
section out of a cylinder—curved horizontally, yet vertically flatter. This allows the screen
to be flatter, but the image can look concave at times. Many newer CRTs have screens that
are curved like a section from a much bigger ball, which makes the screen appear to be flat
to the viewer. These CRTs also have improved the focus of the electron-beam focus that
allows it to travel longer distances. Still other CRTs now have a special glass plate over the
CRT to optically remove the distortion that appears near the edge of the screen of the
flat-screen display.
The flat-panel display avoids all of this by illuminating each pixel equally from behind,
which eliminates the need for a curved screen or any optical effects. Flat-panel monitors
really are flat.Viewable Size
As I mentioned earlier, when it comes to PC monitors, bigger is better. As I will discuss in
more detail later, a bigger monitor provides higher resolutions and better graphics
modes. However, the downside can be that a bigger monitor will also take more room on
your desk, unless you can afford a bigger flat-panel monitor.CRT Display Sizes
CRT monitor sizes are given in what are called nominal sizes. The most popular monitor
sizes are 15-inch, 17-inch, 19-inch, and 21-inch. However, this is the size of the CRT
measured diagonally from a top corner to an opposite bottom corner, case and all (in the
same way a television set is measured and marketed). On a CRT monitor, the case of the
monitor includes a front bezel (the plastic around the edge of the display) that covers up a
smallportionofthedisplayinordertoholditinplace.Thebezelcutsdowntheareaofthe
CRT that can be viewed by as much as a full-inch all of the way around the edge of the
monitor.MostCRTmonitormanufacturersareupfrontaboutthisandwillusuallylistthe
viewable size of the monitor along with the nominal size.
The viewable size of a 17-inch CRT display is actually a bit less than 16 inches. When
comparing monitors, it is good idea to compare the viewable image size rather than the
nominal screen size. You may be surprised that a smaller monitor may be a better value for
yourmoneywhenyoucomparetheprice-per-inchofviewablescreen.Table16-1illustrates
this point by listing the average nominal and viewable screen sizes for CRT monitors.