Stores offer a dizzying variety of monitor choices, from the low-cost units bundled with computers to large-screen tubes that cost more than many systems. Because a monitor can account for a large part of the price of your computer system, you need to know what to look for when you shop for a monitor.

Important factors to consider include

• Viewable image size

• Resolution

• Dot pitch (CRTs)

• Image brightness and contrast (LCDs)

• Power management and safety certifications

• Vertical and horizontal frequencies

• Picture controls

• Environmental issues (lighting, size, weight)

This section helps you understand these issues so you can make a wise choice for your next display, regardless of the display technology you prefer.

The Right Size

CRT-based monitors come in various sizes ranging from 15'' to 42'' diagonal measure. The larger the monitor, the higher the price tag—after you get beyond 19'' displays, the prices skyrocket. The most common CRT monitor sizes are 17'', 19'', and 21''. These diagonal measurements, unfortunately, often represent not the size of the actual image the screen displays, but the size of the tube.

As a result, comparing one company's 17'' CRT monitor to that of another might be unfair unless you actually measure the active screen area. The active screen area refers to the diagonal measure of the lighted area on the screen. In other words, if you are running Windows, the viewing area is the actual diagonal measure of the desktop.

This area can vary widely from monitor to monitor, so one company's 17'' monitor can display a 16'' image, and another company's 17'' monitor can present a 15 1/2'' image. Typically, you can expect to lose 1''–1 1/2'' from the diagonal screen size to the actual active viewing area.

Consult the monitor's packaging, advertising, or manufacturer's Web site for precise information for a given model. For example, ViewSonic lists the size of its G73f CRT monitor as the following: 17'' (16.0'' VIS [viewable image size]). I recommend that you concern yourself with the VIS, not the tube size, when you select a CRT monitor.

You can adjust many better-quality monitors to display a high-quality image that completely fills the tube from edge to edge. Less-expensive monitors can fill the screen also, but some of them do so only by pushing the monitor beyond its comfortable limits. The result is a distorted image that is worse than the monitor's smaller, properly adjusted picture.

In most cases today, the 17'' CRT monitor is the best bargain in the industry. A 17'' monitor is recommended for new systems, especially when running Windows, and is not much more expensive than a 15'' display. I recommend a 17'' monitor as the minimum you should consider for most normal applications.

Displays of 19''–21'' or larger are recommended for high-end systems, especially in situations where graphics applications are the major focus. Larger monitors are particularly handy for applications such as CAD and desktop publishing, in which the smallest details must be clearly visible.

With a 17'' or larger display, you can see nearly an entire 8 1/2''x11'' print page in 100% view; in other words, what you see onscreen virtually matches the page that will be printed. Being able to see the entire page at its actual size can save you the trouble of printing several drafts of a document or project to get it right.

With the popularity of the Internet, monitor size and resolution become even more of an issue. Many Web pages are designed for 800x600 or higher resolutions. Whereas a 15'' monitor can handle 800x600 fairly well, a 17'' monitor set to 1024x768 resolution enables you to comfortably view any Web site without eyestrain (if the monitor supports 75Hz or higher refresh rates) or excessive scrolling.

Resolution

Resolution is the amount of detail a monitor can render. This quantity is expressed in the number of horizontal and vertical picture elements, or pixels, contained in the screen. The greater the number of pixels, the more detailed the images. The resolution required depends on the application.

Character-based applications (such as DOS command-line programs) require little resolution, whereas graphics-intensive applications (such as desktop publishing and Windows software) require a great deal. It's important to realize that CRTs are designed to handle a range of resolutions natively, but LCD panels (both desktop and notebook) are built to run a single native resolution and must scale to other choices.

Older LCD panels handled scaling poorly, but even though current LCD panels perform scaling better, the best results with various resolutions are still found with CRTs. As PC video technology developed, the screen resolutions video adapters support grew at a steady pace.

The Color Graphics Adapter (CGA) and Enhanced Graphics Adapter (EGA) cards and monitors were the first PC graphics standards in the early to mid-1980s. The Video Graphics Array (VGA) standard was released by IBM in April 1987, and all the subsequent resolutions and modes introduced since then have been based on it in one way or another.

VGA mode is still in common use as a reference to the standard 640x480 16-color display that most versions of the Windows operating systems use as their default; Windows XP, however, defaults to SVGA mode, which is 800x600.

The 15-pin connector through which you connect the analog display to most video adapters is also often called a VGA port. A newer 20-pin connector is used for DFP-compatible LCD display panels. A larger 24-pin connector is used on DVI-D displays, whereas DVI-I displays use a 29-pin version of the DVI-D connector.

Nearly all video adapters sold today support SXGA (1280x1024) resolutions at several color depths, and many support UXGA (1600x1200) and higher as well. Typically, in addition to the highest setting your card and display will support, any lower settings are automatically supported as well.

Because all CRT and most new and upcoming LCD displays can handle various resolutions, you have a choice. The combinations of resolution and color depth (number of colors onscreen) you can choose might be limited by how much RAM your graphics adapter has onboard or, if you have motherboard chipset-based video, how much system memory is allocated to your video function.

If you switch to a larger display and you can't set the color depth you want to use, a new video card with more RAM is a desirable upgrade. Video cards once featured upgradeable memory, but this is no longer an option with current models.

Which resolution do you want for your display? Generally, the higher the resolution, the larger the display you will want. Why? Because Windows icons and text use a constant number of pixels, higher display resolutions make these screen elements a smaller part of the desktop onscreen.

By using a larger display (17'' or larger), you can use higher resolution settings and still have text and icons that are readable. To understand this issue, you might want to try various resolutions on your system. As you change from 800x600 to 1024x768 and beyond, you'll notice several changes to the appearance of your screen.

At 800x600 or less, text and onscreen icons are very large. Because the screen elements used for the Windows desktop and software menus are at a fixed pixel width and height, you'll notice that they shrink in size onscreen as you change to the higher resolutions. You'll be able to see more of your document or Web page onscreen at the higher resolutions because each object requires less of the screen.

If you are operating at 800x600 resolution, for example, you should find a 15'' monitor to be comfortable. At 1024x768, you probably will find that the display of a 15'' monitor is too small; therefore, you will probably prefer to use a larger one, such as a 17'' monitor.

Although these are not necessarily the limits of a given monitor's capabilities, they are what I recommend. On small monitors set to high resolutions, characters, icons, and other information are too small for most users and can cause eyestrain. Low-cost CRT monitors and those bundled with many systems often produce blurry results when set to their maximum resolution and often have low refresh rates at their highest resolution.

Whereas CRTs can produce poor-quality results at very high resolutions, LCD displays are always crisp and perfectly focused by nature. Also, the dimensions advertised for the LCD screens represent the exact size of the viewable image, unlike most conventional CRT-based monitors.

In addition, the LCD is so crisp that screens of a given size can easily handle resolutions that are higher than what would otherwise be acceptable on a CRT. For example, many of the high-end notebook systems now use 14'' or 15'' LCD panels that feature SXGA+ (1400x1050) or even UXGA (1600x1200) resolution.

Although these resolutions would be unacceptable on a CRT display of the same size, they work well on the LCD panel built in to the laptop because of the crystal-clear image and because you generally sit closer to a laptop display. In fact, it is for this reason that such high resolutions might not work on desktop LCD panels unless they are larger 17'' or 18'' models.

Dot Pitch (CRTs)

Another important specification that denotes the quality of a given CRT monitor is its dot pitch, which is controlled by the design of the shadow mask or aperture grille inside the CRT. A shadow mask is a metal plate built into the front area of the CRT, next to the phosphor layers.

It has thousands of holes that are used to help focus the beam from each electron gun so that it illuminates only one correctly colored phosphor dot at a time. Because of the immense speed of screen rewriting (60–85 times per second), all dots appear to be illuminated at the same time. The mask prevents the electron gun from illuminating the wrong dots.

The original IBM PC color monitor had a dot pitch of .43mm, which is considered to be poor by almost any standard. Smaller pitch values indicate sharper images. Most monitors have a dot pitch between .25mm and .30mm, with state-of-the-art monitors down to .24mm or less.

To avoid grainy images, look for a dot pitch of .26mm or smaller. Be wary of monitors with anything larger than a .28mm dot pitch; they lack clarity for fine text and graphics. Although you can save money by buying monitors with smaller tubes or a higher dot pitch, the trade-off isn't worth it.

Monitors based on Sony's Trinitron picture tubes and Mitsubishi's DiamondTron picture tubes use an aperture grille, which uses vertical strips (rather than a shadow mask) to separate red, green, and blue phosphors. This produces a brighter picture, although the stabilizing wires shown in Figure below are visible on close examination.

Monitors using an aperture grille–type picture tube use a stripe pitch measurement instead of dot pitch. An aperture grille monitor stripe pitch of .25mm is comparable to a .27mm dot pitch on a conventional monitor.

Some of NEC's monitors use a variation on the aperture grille called the slotted mask, which is brighter than standard shadow-mask monitors and more mechanically stable than aperture grille–based monitors. The dot pitch or stripe pitch measurement is one of the most important specifications of any monitor, but it is not the only specification.

You might find the image on a monitor with a slightly higher dot pitch superior to that of a monitor with a lower dot pitch. There is no substitute for actually looking at images and text on the monitors you're considering purchasing.

Image Brightness and Contrast (LCD Panels)

As previously mentioned, dot pitch is not a factor in deciding which LCD panel to purchase. Although it's a consideration that applies to both LCDs and CRTs, the brightness of a display is especially important in judging the quality of an LCD panel.

Although a dim CRT display is almost certainly a sign of either improper brightness control or a dying monitor, brightness in LCD panels can vary a great deal from one model to another. Brightness for LCD panels is measured in candelas per square meter, which is abbreviated "nt" and pronounced as a nit.

Typical ratings for good display panels are between 200 and 400 nits, but the brighter the better. A good combination is a rating of 250 nits or higher and a contrast rating of 300:1 or higher.

Interlaced Versus Noninterlaced

Monitors and video adapters can support interlaced or noninterlaced resolution. In noninterlaced (conventional) mode, the electron beam sweeps the screen in lines from top to bottom, one line after the other, completing the screen in one pass. In interlaced mode, the electron beam also sweeps the screen from top to bottom, but it does so in two passes—sweeping the odd lines first and the even lines second.

Each pass takes half the time of a full pass in noninterlaced mode. Early high-resolution monitors, such as the IBM 8514/A, used interlacing to reach their maximum resolutions, but all recent and current high-resolution (1,024x768 and higher) monitors are noninterlaced, avoiding the slow screen response and flicker caused by interlacing.

Energy and Safety

Monitors, like virtually all power-consuming computer devices, have been designed to save energy for a number of years. Virtually all monitors sold in recent years have earned the Environmental Protection Agency's Energy Star logo by reducing their current draw to 30 watts or less when idle.

Power-management features in the monitor, as well as controls provided in the system BIOS and in the latest versions of Windows, help monitors and other types of computing devices use less power.

Power Management

One of the first energy-saving standards for monitors was VESA's Display Power-Management Signaling (DPMS) spec, which defined the signals a computer sends to a monitor to indicate idle times. The computer or video card decides when to send these signals.

In Windows 9x/Me/2000/XP, you must enable this feature if you want to use it because it's turned off by default. To enable it in Windows 9x/Me, open the Display properties in the Control Panel, switch to the Screen Saver tab, and make sure the Energy Star low-power settings and Monitor Shutdown settings are checked.

You can adjust how long the system remains idle before the monitor picture is blanked or the monitor shuts down completely. Use the Power icon in Windows 2000/XP to set power management for the monitor and other peripherals. You can also access power management by selecting the Screen Saver tab on the Display properties sheet and clicking the Power button.

Intel and Microsoft jointly developed the Advanced Power Management (APM) specification, which defines a BIOS-based interface between hardware that is capable of power-management functions and an operating system that implements power-management policies.

In short, this means you can configure an OS such as Windows 9x to switch your monitor into a low-power mode after an interval of nonuse and even to shut it off entirely. For these actions to occur, however, the monitor, system BIOS, and operating system must all support the APM standard.

With Windows 98, Windows Me, Windows 2000, and Windows XP, Microsoft introduced a more comprehensive power-management method called Advanced Configuration and Power Interface (ACPI). ACPI also works with displays, hard drives, and other devices supported by APM and allows the computer to automatically turn peripherals, such as CD-ROMs, network cards, hard disk drives, and printers, on and off.

It also enables the computer to turn consumer devices connected to the PC, such as VCRs, televisions, telephones, and stereos, on and off. Although APM compatibility has been standard in common BIOSs for several years, a number of computers from major manufacturers required BIOS upgrades to add ACPI support when Windows 98 was introduced.

Virtually all monitors with power management features meet the requirements of the United States EPA's Energy Star labeling program, which requires that monitor power usage be reduced to 15 watts or less in standby mode. However, some current monitors also comply with the far more stringent Energy 2000 (E2000) standard developed in Switzerland. E2000 requires that monitors use less than 5 watts when in standby mode.

Emissions

Another trend in green monitor design is to minimize the user's exposure to potentially harmful electromagnetic fields. Several medical studies indicate that these electromagnetic emissions can cause health problems, such as miscarriages, birth defects, and cancer.

The risk might be low, but if you spend a third of your day (or more) in front of a computer monitor, that risk is increased. The concern is that VLF (very low frequency) and ELF (extremely low frequency) emissions might affect the body. These two emissions come in two forms: electric and magnetic.

Some research indicates that ELF magnetic emissions are more threatening than VLF emissions because they interact with the natural electric activity of body cells. Monitors are not the only culprits; significant ELF emissions also come from electric blankets and power lines.

Today, virtually all monitors on the market support TCO standards. If you aren't using a low-emission monitor yet, you can take other steps to protect yourself. The most important is to stay at arm's length (about 28 inches) from the front of your monitor.

When you move a couple of feet away, ELF magnetic emission levels usually drop to those of a typical office with fluorescent lights. Likewise, monitor emissions are weakest at the front of a monitor, so stay at least 3 feet from the sides and backs of nearby monitors and 5 feet from any photocopiers, which are also strong sources of ELF.

Electromagnetic emissions should not be your only concern; you also should be concerned about screen glare. In fact, some of the antiglare panels that fit in front of a monitor screen not only reduce eyestrain, but also cut ELF and VLF emissions. Note that because plasma and LCD displays don't use electron guns or magnets, they don't produce ELF emissions.

Frequencies

One essential buying decision is to choose a monitor that works with your selected video adapter. Today, virtually all monitors are multiple-frequency (also called multiscanning and multifrequency) units that accommodate a range of standards, including those that are not yet standardized. However, big differences exist in how well various monitors cope with various video adapters.

Controls

Most of the newer CRT monitors and LCD panels use digital controls instead of analog controls. This has nothing to do with the signals the monitor receives from the computer, but only the controls (or lack of them) on the front panel that enable you to adjust the display.

Monitors with digital controls have a built-in menu system that enables you to set parameters such as brightness (which adjusts the black level of the display), contrast (which adjusts the luminance of the display), screen size, vertical and horizontal shifts, color, phase, and focus.

A button brings the menu up onscreen, and you use controls to make menu selections and vary the settings. When you complete your adjustments, the monitor saves the settings in nonvolatile RAM (NVRAM) located inside the monitor.

This type of memory provides permanent storage for the settings with no battery or other power source. You can unplug the monitor without losing your settings, and you can alter them at any time in the future. Digital controls provide a much higher level of control over the monitor and are highly recommended.

Although LCD panels aren't affected by geometry errors as CRT monitors can be, they can have their own set of image-quality problems, especially if they use the typical 15-pin analog VGA video connector. Pixel jitter and pixel swim (in which adjacent pixels turn on and off) are relatively common problems that occur when using an LCD monitor connected to your PC with an analog VGA connector.

Environment

One factor you might not consider when shopping for a monitor is the size and strength of the desk on which you intend to put it. Although many 17'' CRT monitors use less desk space than before, reducing the 18''–24'' depth used by older models to a more reasonable 16''–17'' depth, these monitors are still relatively heavy at around 35–40 lbs.

21'' and larger monitors can be truly huge, weighing in at 60 lbs. or more! Some of the rickety computer stands and mechanical arms used to keep monitors off the desktop might not be capable of safely holding or supporting a large unit.

Check the weight rating of the computer stand or support arm you're planning to use before you put a CRT monitor on it. It's tragic to save a few dollars on these accessories, only to watch them crumple under the weight of a large monitor and wipe out your monitor investment.

Another important consideration is the lighting in the room in which you will use the monitor. The appearance of a CRT display in the fluorescent lighting of an office is markedly different from that in your home. The presence or absence of sunlight in the room also makes a big difference.

Office lighting and sunlight can produce glare that becomes incredibly annoying when you are forced to stare at it for hours on end. You can reduce onscreen glare by choosing monitors equipped with flat-square or other flat CRT technologies or LCD panels and antiglare coatings. You can retrofit aftermarket filters to monitors that lack these features to help reduce glare.

Testing a Display

Unlike most of the other peripherals you can connect to your computer, you can't really tell whether a monitor suits you by examining its technical specifications. Price might not be a reliable indicator either. Testing monitors is a highly subjective process, and it is best to "kick the tires" of a few at a dealer showroom or in the privacy of your home or office (if the dealer has a liberal return policy).

Testing should also not be simply a matter of looking at whatever happens to be displayed on the monitor at the time. Many computer stores display movies, scenic photos, or other flashy graphics that are all but useless for a serious evaluation and comparison.

If possible, you should look at the same images on each monitor you try and compare the manner in which they perform a specific series of tasks. Before running the tests listed here, set your display to the highest resolution and refresh rate allowed by your combination of display and graphics card.

One good series of tasks is as follows:

• Draw a perfect circle with a graphics program. If the displayed result is an oval, not a circle, this monitor will not serve you well with graphics or design software.

• Using a word processor, type some words in 8- or 10-point type (1 point equals 1/72''). If the words are fuzzy or the black characters are fringed with color, select another monitor.

• Display a screen with as much white space as possible and look for areas of color variance. This can indicate a problem with only that individual unit or its location, but if you see it on more than one monitor of the same make, it might indicate a manufacturing problem.

It could also indicate problems with the signal coming from the graphics card. Move the monitor to another system equipped with a different graphics card model and retry this test to see for certain whether it's the monitor or the video card.

• Display the Microsoft Windows desktop to check for uniform focus and brightness. Are the corner icons as sharp as the rest of the screen? Are the lines in the title bar curved or wavy? Monitors usually are sharply focused at the center, but seriously blurred corners indicate a poor design.

Bowed lines can be the result of a poor video adapter, so don't dismiss a monitor that shows those lines without using another adapter to double-check the effect. Adjust the brightness up and down to see whether the image blooms or swells, which indicates the monitor is likely to lose focus at high brightness levels. You can also use diagnostics that come with the graphics card or third-party system diagnostics programs to perform these tests.

• With LCD displays in particular, change to a lower resolution from the panel's native resolution using the Microsoft Windows Display properties settings. Because LCD panels have only one native resolution, the display must use scaling to handle other resolutions full-screen.

If you are a Web designer, are a gamer, or must capture screens at a particular resolution, this test will show you whether the LCD panel produces acceptable display quality at resolutions other than normal. You can also use this test on a CRT, but CRTs, unlike LCD panels, are designed to handle a wide variety of resolutions.

• A good monitor is calibrated so that rays of red, green, and blue light hit their targets (individual phosphor dots) precisely. If they don't, you have bad convergence. This is apparent when edges of lines appear to illuminate with a specific color. If you have good convergence, the colors are crisp, clear, and true, provided there isn't a predominant tint in the phosphor.

• If the monitor has built-in diagnostics (a recommended feature), try them as well to test the display independently of the graphics card and system to which it's attached.