The Big Picture
Monitor manufacturers typically offer entry-level 17- or 19-inch LCD models that combine very low prices with pared-down features. (For example, many of the inexpensive PC deals you see from Dell include a monitor that has only an analog video input, not a digital one.) Such monitors work well enough for Web surfing, e-mail, and other office tasks--as long as they provide adequate resolution and screen adjustment controls for brightness, color, and other settings. Midrange and professional lines often provide better image quality through digital connections (predominantly DVI, though some models now support DisplayPort, too) and extensive features, such as superior image-adjusting controls, integrated USB ports and memory card slots, a larger set of ergonomic options (such as height adjustment or the ability to pivot), and higher resolutions. Some professional-level monitors include asset control--to help IS managers keep track of their company's property via a LAN--and hardware calibration, which adjusts the monitor and/or graphics card to ensure precise hues. Other pro LCDs provide color-calibration tools, as well.
LCD vs. CRT
LCD is clearly the dominant display technology today. Historically, graphics professionals have preferred CRT monitors because they support a greater range of resolutions (including very high resolutions) and show truer colors and greater nuance in color. However, manufacturers ceased making the aperture-grille models--generally agreed to be the top-performing type of CRT for photos and general graphics work--in 2005. Many pros now use high-end LCDs, which approach the color quality of CRTs yet consume much less energy. The development of color-calibrating hardware and software specifically designed for LCDs has helped persuade many professionals to make the switch to flat panels. Continuing improvements in black level (perfect black--which is traditionally somewhat soft or grayed in LCDs) and the use of both LED backlighting and a wider color gamut are easing the shift toward LCD for professional users.
People who work mostly with text have always gravitated toward LCDs because pixels on an LCD have well-defined edges, resulting in sharply focused letters. Gamers have appreciated CRT technology's fast response time, but current-generation LCDs can refresh quickly enough to make them game-worthy for most users. Some LCD models go so far as to feature faster refresh rates specifically for gaming.
Native resolution: Because an LCD uses a matrix of pixels to display its image, it has a fixed (or "native") resolution at which the display looks best. Most 17-, 18-, or 19-inch models use a 1280-by-1024-pixel native resolution. Wide-screen 23- and 24-inch models usually have a native resolution of 1920 by 1200, and 30-inch wide-screens have a resolution of 2560 by 1600. If you set the monitor to a lower-than-native resolution--to upsize very small text, for instance--the image will almost certainly be less defined, because the display will use only a portion of the pixels it contains and will scale up the resulting image to fill the screen. Keep in mind that you can never exceed the native resolution of an LCD monitor. For example, you will not be able to display 1600 by 1200 resolution on an LCD with a native resolution of 1280 by 1024.
Though scaling technologies have improved in recent years, you're still likely to be disappointed with their results, so a particular LCD is a good choice if its native resolution is one you are comfortable using for all applications. In the PC World Test Center, we test all monitors at their native resolution.
Aspect ratio: Wide-screen monitors with a 16:10 aspect ratio have been dominant in the past, but over the last year the industry has started moving toward a true 16:9 wide-screen aspect ratio, as you'd find on an HDTV. The wide-screen format is a productivity enhancer, as it's useful for working in large spreadsheets or in programs such as Adobe Photoshop that contain many toolbars or palettes; you can also view documents side-by-side (on a 24-inch display, for example, you can get two Web pages to show next to each other). The format is appealing for watching DVDs as well, although the image quality may not be as good as on a TV. Many users see a wide-screen monitor as an upgrade from smaller dual monitors. A dual-monitor setup is usually the less expensive proposition; that approach, however, requires that your graphics card support a dual-display setup (some do so through VGA, which means that your monitor must have a VGA port, and your content will have to come through an analog, not digital, connection).
A couple of important things to keep in mind: An LCD's screen size is measured diagonally, and the area of a wide-screen monitor's display is smaller than that of a regular-format display of the same size. In other words, a 21-inch wide-screen monitor shows about as many pixels as you'd expect from a regular-format 19-inch monitor. Also, with LCDs, the stated diagonal is always the true measurement of the viewable screen. In the days of CRT monitors, vendors would state a tube size as, say, 21 inches, but the diagonal of the viewable screen would be from 1 to 2 inches less.
Viewing angle: Measured in degrees (up to 180), an LCD's viewing angle indicates how far you can move to the side (or above, or below) from the center of the display before the image quality deteriorates to unacceptable levels. No matter what size monitor you use, a wide viewing angle becomes increasingly important the more you care about getting accurate, consistent colors for design work or for tweaking digital photos. Each vendor determines its own criteria for this, as no industry-standard method has been established for measuring viewing angle. As a result, the numbers may not be comparable from one vendor to another, but they can indicate relative performance among models from the same company.
The best way to judge horizontal viewing angle is to see the monitor for yourself. Most monitors have a viewing angle of at least 160 degrees; if you encounter a monitor whose viewing angle is below 150 degrees, eliminate it from consideration. The larger the monitor, the more important a wide viewing angle is. On monitors measuring 17 inches or more, the edge of the screen is at a greater angle to someone sitting directly in front of its center, and people are more likely to be able to share the monitor when working or giving a group presentation.
Contrast ratio: This term refers to the difference in light intensity between the brightest white and the darkest black that an LCD can produce. Look for a contrast ratio of 400:1 or better--with anything lower, colors may wash out when you turn up the brightness and may disappear when you turn it down. Higher is better only up to a point, however. Contrast ratios over 600:1 are unlikely to provide any advantage, and monitor vendors are likely using "fuzzy math" to calculate those values, anyway.
The rated contrast ratio is often a poor indicator of performance; because no industry-standard measurement exists, it can vary from vendor to vendor. Since shoppers have no way to tell if the manufacturer has overstated or understated the contrast ratio, the specification is essentially useless for comparison purposes.
Brightness: Expressed as candelas per square meter (cd/m2) or nits, this specification measures the greatest amount of light that comes from a screen displaying pure white. Most LCDs have a brightness level of 250cd/m2 or greater, which should be more than sufficient. Vendors usually set the brightness level to maximum on new monitors to impress customers. High brightness can be eye-catching for video and graphics, but it can be uncomfortable over time, particularly for text viewing--and it may cause photographic nuances to wash out. Fortunately, all monitors offer brightness adjustments beyond the default settings, and many monitors provide screen modes that change the brightness (and sometimes the color and other characteristics) to make certain types of content look best.
Digital versus analog: Digital always trumps analog, but now you have a choice of digital connectors in the monitor world. DVI remains the most pervasive display connector across graphics cards, motherboards, and monitors, so if you have a graphics card with a digital video output--and if you bought a desktop in the past few years, you probably do--choose an LCD that has DVI digital input. The image won't have to convert from analog to digital and back again, so it will be clearer. Most digital-capable monitors also have a VGA (analog) connection, which is useful if you're considering a dual-monitor setup. You can find two types of DVI connections on typical LCD monitors: DVI-D and DVI-I. DVI-D is a digital-only port, while DVD-I can accept either an analog input or a digital one (you'll need a special connector to hook up to your PC's VGA analog port, however). Very few laptop PCs come with DVI outputs for external monitors, but some laptops can gain a DVI connection when they attach to a docking station or port replicator.
Some newer monitors--notably from Apple and Dell--use a DisplayPort connector instead of DVI. DisplayPort, a relatively new standard for display connections backed by Apple, Dell, HP, Philips, Samsung, Lenovo, AMD, Intel, nVidia, and other companies, is still rare and remains an uncommon output on PCs, motherboards, and graphics cards. Apple's 2008 refresh of its MacBook laptops introduced DisplayPort connectivity, though. HDMI (High-Definition Multimedia Interface) connectors are becoming increasingly common on large (22-inch and greater) LCDs. Not surprisingly, this interface--the same as you use on an HDTV--is increasingly available on graphics cards, motherboards, and laptops. HDMI has the advantage of transmitting both digital video and audio signals between devices.
Special inputs: As users perform more video and photo editing at their PCs--and as more people watch DVDs on them--more monitors offer inputs that we used to see only on TVs or peripherals. Photographers and videographers may be interested in S-Video ports and memory card slots; DVD aficionados may want to keep their eyes peeled for monitors with component and/or composite inputs, or even HDMI ports for use with a Blu-ray Disc player or a gaming console.
Response time: Pixel response time governs the time (measured in milliseconds) required for a pixel to change. In theory, a low response time signifies an LCD with minimal motion artifacts in moving images. This spec is especially important to video watchers and gamers.
There are two main types of LCD response time. Rise-and-fall response time measures the time it takes a pixel to turn from black to white (rise) and back to black (fall). Gray-to-gray response time measures the time it takes for a pixel to change from one shade of gray to another. Each type has its uses.
Rise-and-fall response time has been clearly defined and has been an industry standard for years. As of yet, no such definition for gray-to-gray response time exists. In theory, gray-to-gray response time could be a useful spec, since it can measure the time required to switch between shades (as opposed to black and white). This should make it useful for indicating how an LCD will look showing the subtle shades of movies and games. However, the lack of an agreed-upon definition--the same issue that plagues contrast ratio--means that vendors may use different ways of determining the spec, so response-time specs are not always comparable from vendor to vendor. That said, most LCD monitors available today have fast enough response rates for all but the most hard-core gamers.
Size: Though it may seem obvious, bear in mind the size of your workspace when deciding on the type of monitor to buy. A huge monitor may look appealing, but you want to make sure your desk is deep enough to let you view it from a comfortable distance.
Physical adjustments: Almost all monitors come with tilt adjustment. If you spend a great deal of time in front of your monitor, you may want to find one that lets you adjust the height of the screen as well. You may find that it's worth a few extra dollars to get a monitor that will keep the screen at a comfortable height instead of making your neck do all the work. A monitor with side-to-side swivel adjustment makes it easier to show your screen to a nearby customer or coworker. Finally, if you need to view anything that's longer than it is tall--a full-page document, a deep Web page, or a screen full of e-mail--you could get a lot of use out of a screen-pivot function. Not every monitor with a pivoting screen includes image-pivoting software; you'll need that to make your screen adjust to portrait mode.