Many displays use Trinitron or Diamondtron technology. In these displays, pixels are arranged in vertical stripes. These designs rely on the precision of the electron gun for horizontal separation, so the mask (called an aperture grille in these displays) only has to keep the vertical stripes separate. Aperture grilles require half as much metal as traditional shadow masks, so the end result is that they block fewer phosphors and that the display can be extremely bright with vivid colors and excellent contrast. You can tell if a monitor uses an aperture grille by looking for a thin horizontal line a few inches from the top of the screen and a few inches from the bottom that resembles a pencil mark. This is the shadow cast by a thin damper wire that keeps all the vertical aperture grille "strips" from moving around.

Some monitors have Invar shadow masks. Invar is a special alloy that resists expansion when exposed to high temperatures. Theoretically, this allows displays with Invar shadow masks to run at higher brightness settings with better contrast since the mask is less likely to expand and cause image distortion. Because image quality has more to do with overall engineering quality than the use of an exotic alloy, don't hesitate to buy a display without Invar if you like its output.

If you see a specification for stripe pitch instead of dot pitch, the monitor is using a Trinitron or Diamondtron tube. Stripe pitch is the distance, in millimeters, between two like-colored stripes. Lower numbers are better, but a stripe pitch of 0.22 is not necessarily better than a dot pitch of 0.25. The two values shouldn't be directly compared.

Another nice aspect of a flat-panel display is its digital nature. When you use this display in an all-digital environment, you can get terrific accuracy in imaging. For example, if you send a digital signal for a certain shade of green, your monitor will always produce that precise shade of green on the LCD display. CRTs, on the other hand, are less accurate.

LCDs are backlit, and that light has to pass through a few polarization filters and other layers before it finally emerges from the front of the display. This is why most LCDs are not as bright as a good CRT. It also explains why LCDs are practically illegible when you view them from any angle other than the straight on.

Older CRTs have a pronounced curvature to their screens. This allows the electron beams to travel the same distance to each phosphor. Like a flashlight beam, electron beams disperse over a distance, and using a truly flat screen could lead to distortion at the edge of the display. For this reason most older CRT displays represent a section of a sphere, where all points are equidistant from the origin of the electron beams. Trinitron tubes (and other displays that employ an aperture grille) represent a section of a cylinder, meaning they are flat vertically but curved somewhat horizontally. This explains why images from these types of devices sometimes seem concave.

Advances in technology allow for tighter electron-beam focus over longer distances in the newer CRT screens. This allows the source of the electron beams to be farther from the edges of the display than from the center. These newer CRTs still represent a section of a sphere, but the sphere is just very large so that the display appears nearly flat to a user. Some manufacturers have augmented this effect by affixing special glass plates to the front of the tube. The glass reverses optical distortion near the edges of the screen so the final image projected to a user's eyes appears flat and crisp from corner to corner.

True flat-panel displays rely on none of this optical trickery. For example, in a TFT LCD, the light source behind the display illuminates each pixel equally and constantly (theoretically at least), so the design doesn't need to incorporate any curvature. The bottom line is that flat-panel displays really are flat.

Listed LCD screen sizes generally are accurate, so a 15-inch LCD is closer in viewable image size to a 17-inch CRT than a 15-inch CRT.

Don't pay any attention to CRTs with small screen sizes that claim high resolutions are possible. Even if a new 17-inch monitor might be capable of a resolution of 1,600 x 1,200, you'll never use it. A screen that small running at such a high resolution would display microscopic text, tiny desktop icons, and take such a hit in image quality that it would be of no practical value. The upper usable limit of a 17-inch monitor usually is 1,280 x 1,024, but many users run them at 1,024 x 768. A reasonable upper limit for a 19-inch CRT is 1,280 x 1,024. You can run a 21-inch monitor successfully at 1,600 x 1,200.

Flat-panel display resolution works differently. LCDs and most other flat-panel technologies have a fixed resolution. When you select a resolution that is outside the native resolution, image degradation occurs. LCDs are notoriously poor at enlarging and shrinking images, so you should buy one only if you plan to work at the same resolution all the time.

Most LCDs are capable of only an 18-bit color depth, or slightly more than 262,000 simultaneous colors. Some new designs can simulate 24-bit color. This is something to consider if you plan to play games or work with images that use 24-bit or higher color depths.

If you are buying an LCD display, forget about the refresh rate. Because of the way LCD technology works, it can provide stable images at 60 Hz, and sometimes less.

All LCDs are digital devices, but until recently, they universally employed analog interfaces. This was because, in the past, all video cards were designed for use with CRT monitors. The video card sends digital information to its digital-to-analog converter (DAC), which transmits the resulting analog signal down the cable to the monitor. CRTs can use this information as-is, but all-digital LCDs must run the analog signal through the monitor's analog-to-digital converter. This can lead to image degradation. Try to find an LCD that uses a digital interface, but make sure you have a video card capable of digital output, or the display will suffer.