Display quality, the most important monitor feature, isn't a major worry thanks to a generally high standard of performance. But you should also consider these factors when choosing a monitor.
A monitor's resolution refers to the number of picture elements, or pixels, that make up an image. More pixels means finer detail. Most monitors can display at several resolutions, generally from 640x480 to 1920x1200, depending on the monitor and the computer's graphics card. An LCD usually displays its sharpest image when set to its "native" resolution--typically 1440x900 for a 19-inch display, 1680x1050 for a 22-inch, and 1920x1200 for a 24-inch. Typical resolutions for wide-screen monitors are 1600x900 for a 20-inch, 1920x1080 for a 22-inch, and 1920x1200 for a 24-inch. The Apple display we tested has resolution of 2560x2440.
The higher the resolution, the smaller the text and images, meaning more content can fit on the screen. Higher resolution is better for working with photos and graphics.
A flat-panel display's response time indicates how quickly the screen can respond to video image transitions.
Expressed as a ratio, this is a measure of the difference between the brightest white and the deepest black. A higher contrast ratio can produce images that are more vivid and punchy. But because the way manufacturers measure contrast ratio is not uniform, advertised figures are not reliable.
A bright screen is important if you're working in a brightly lit room. The spec is expressed as candelas per square meter, or cd/m2. The higher the number, the better. You can also control an LCD's brightness with buttons or on-screen controls. Most monitors also have controls for color balance (usually called color temperature), adjusting the screen geometry, and similar functions.
Virtually all new monitors have the DVI (digital visual interface) ports you need to take advantage of higher-end video cards for a sharper image. Not all include the necessary DVI cable, however (you can buy one for about $10). HDMI (high-definition multimedia interface) ports are becoming more prevalent. You'll also find them on some newer computers and electronics equipment such as Blu-ray/DVD players. One of the advantages of the HDMI interface is it allows for video and audio to be sent over the same cable (useful only if the monitor has built-in speakers). If you choose a monitor without one, you can buy an adapter for $25 or less that turns a DVI port into an HDMI connector, but you won't get audio through it.
DisplayPort is another connector beginning to show up on monitors. It can provide the same functionality as HDMI, but because it is royalty-free, it costs less for manufacturers to use it. Last year, several computer and display makers said they would eventually replace DVI and VGA connectors with DisplayPort and HDMI ports.
Another feature you'll be seeing on more monitors is touch-screen technology. The touch-screen monitors we've tested already work with the touch capabilities built into Windows 7. What's more important to consider is what's coming with Windows 8, which is being developed with tablets and computers in mind. That new operating system will incorporate a lot of touch-screen features into its new interface, which will include a series of tiles that represent your applications, documents, and so on. Windows 8 is due out this fall.
You'll find this feature on a few new monitors. All of the 3D monitors in our Ratings use active 3D technology, which generally does a much better job maintaining the 3D effect at various viewing angles than displays that use passive 3D technology. In our tests, all produced great-looking 3D images. The picture on an active 3D monitor isn't quite as bright in 3D mode as it is on a passive display. You'll need special glasses to view 3D. Compared with glasses for passive 3D, active-3D glasses tend to be heavier, cost more, and might need batteries. Of the monitors in our Ratings, only the Acer HN274H ($680) came with glasses.
Some monitors include a microphone, one or more USB ports, integrated or separate speakers, and HDMI inputs for viewing the output of a Blu-ray player or camcorder. You may also see LCD monitors with memory-card readers, so you can display photos on-screen directly from a camera, and iPod docks for viewing images or playing music through the monitor. A built-in TV tuner is another feature to look for if you want your monitor to double as a TV.