Monitor buying guide

Now that we've covered panel and backlight technologies, other specifications and features should factor into your buying decision. Here are the most important ones. Be warned, the vendor will not quote all of these specifications and you may have to rely on reviews--like the ones at CNET--to get the details on them.

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Movies shot in 2.35:1 (like "Iron Man") are always letterboxed, whether on 16:9 or 16:10 monitors, unless you zoom the image.

Essentially, a 16:9 monitor can display a full-screen 16:9 Blu-ray or digital movie shot in 1.85:1 without stretching the image to fit the screen. A 16:10 monitor will need to stretch the same movie's image a bit to get it to full screen without any black bars.

Black Level: No display can show black without some light seeping through. Black level is a measurement of how much light emanates from the display while showing black.

Brightness: A measurement of how much light a panel can produce. Luminance is expressed in candelas per square meter (cd/m2). A measurement of 200 to 250 cd/m2) is OK for most productivity tasks; 300 to 400 cd/m2 is great for movies and games.

Contrast ratio: The difference in light intensity between the brightest white and the deepest black.

Though contrast ratios typically don't exceed 1,000:1 on monitors, lately, manufactures have been pushing dynamic contrast as a spec, and sometimes misleadingly calling it contrast ratio.

Before a monitor is released to the public, panels go through testing in the vendor's own lab. These tests produce the specs that the vendor will then publish with the release of the monitor. Specs such as maximum brightness, pixel pitch, pixel response time, contrast ratio, and dynamic contrast ratio are all determined in the vendor's lab.

When testing normal contrast ratio, vendors use a device that measures luminance to determine how much light is emanating from a display while it's showing both a completely black and a completely white screen. They then take each number, do a bit of math, and come up with the contrast ratio.

Now, aside from a relatively low number of LCDs that use LED-backlighting technology, all LCDs have a lamp built into their screens. When you turn your brightness setting down, you're actually just dimming the lamp in the back. When the vendors dim the backlight to get the contrast ratio score, they dim it to a point, but do not turn it off.

When they test to get the readings for dynamic contrast, however, they turn off the backlight.

With the backlight off, the darkness of the black level increases by a factor of 10 or more. At this point, the vendor takes its reading for the dark screen and compares it with the white screen reading it recorded earlier. Since this new dark screen level is so dark, it increases the contrast ratio. The problem is that the screen only gets this dark when the video signal is black or near black--not very useful when you're watching a movie, or playing a game, or doing pretty much anything. The primary reason for including this feature is that the contrast ratio goes from 1,000:1 to 10,000:1, and even 30,000:1.

When vendors push dynamic contrast as a spec for LCDs that use LED-backlighting technology, however, it may be more appropriate. Direct contrast ratio works differently with LEDs than with lamp-based LCDs. When a portion of an image in a movie is relatively dark, the LEDs in that local area of the screen are dimmed. This occurs on a frame-by-frame basis and lowers the black level in that dark area only. Unfortunately, this implementation has its weaknesses, as well, as there can be some noticeable visual glitches in the areas that darken.

Bottom line? Take all measured specs with a grain of salt; however, take dynamic contrast specs with a huge bucketload of salt.

DisplayPort: Heralded as the successor to DVI and HDMI, DisplayPort is a higher-bandwidth connection that could facilitate thinner and lighter monitors as they would no longer require special circuitry (and hardware to run that circuitry) to receive video signal. While we saw an increased adoption of DisplayPort among mobile PCs and graphics cards in 2011, the monitor segment is still only slowly ramping up support for the technology, thanks to comparatively low profit margins and the industry's reliance on legacy ports like VGA.

DVI: Some newer monitors forgo including digital visual interface (DVI) in favor of HDMI. If this is the case with the monitor you're interested in, make sure the monitor includes a DVI-to-HDMI cable or that your video card supports an HDMI connection. Having said that, we recommend getting a monitor with at least one DVI connection.

HDMI: An HDMI connection is used to connect the display to a high-definition source, such as a Blu-ray player, video game system, or a DVR-based HD cable/satellite set-top box. HDMI connections have become more common recently and it's the exception now when a monitor, 22 inches and larger, doesn't have one. If you're planning to use your monitor as a television, this is an essential feature.

Pixel-response rate: This refers to how quickly a pixel can change colors, measured in milliseconds (ms); the lower the milliseconds, the faster the pixels can change, thus reducing the ghosting or streaking effect you might see in a moving or changing image. Based on new evidence, however, it's likely you won't see any streaking or ghosting in a modern LCD when watching a movie.

Input lag: A delay in which the LCD's image lags behind what's been sent to the screen. Not everyone notices input lag, and vendors rarely, if ever, quote this figure for their monitors. Input lag affects gamers the most. If split-second reactions are paramount in your gaming sessions, do some research as to a monitor's input lag before you buy.

Ergonomic options: Most LCDs offer some degree of screen tilt, usually 30 degrees back and 5 degrees forward. Some include a swivel feature, many offer height adjustability, and some panels can also pivot between portrait and landscape modes, making legal-size documents and Web pages easier to view. Some LCDs can be attached to VESA-compatible mounts that connect to third-party wall mounts or swinging arms.

Resolution: Dictated by screen size, aspect ratio, and sometimes the manufacture's digression. Make sure you are comfortable with an LCD's native resolution before you buy it. Remember, an LCD that scales its image to a non-native resolution will never look as good.

Memory card readers: A few monitors have media card readers built into the bezels. This is a handy addition for digital photo enthusiasts who want to see their pictures without using a PC.

USB: Many displays have USB ports. Typically, they are not powered hubs, but simply convenient ports to connect low-powered devices such as a keyboard or a mouse, thereby reducing the tangle of cables that run back to the computer.

Audio: Some monitors offer audio functions, either as standard items or as optional accessories. These may include a headset jack, a volume control, or embedded speakers. In general, these speakers are of limited quality, and an inexpensive $30 speaker set from an office-supply or computer store will often provide much better sound.

Viewing angle: Largely dictated by panel technology. The physical structure of LCD pixels can cause the brightness and even the color of images to shift if you view them from an angle rather than facing the screen directly. Take manufacturers' specifications with a grain of salt and make your own observations, if possible.

HDTV: As work and entertainment products continue to converge, many monitors now have features designed to take advantage of television and movie content. Some include TV tuners and connectors for video signals from cable television systems or antennas. Many new monitors are simply HDTVs in disguise.