With screen sizes no bigger than a mainstream notebook, USB-powered displays such as the Lenovo ThinkVision LT1421 and AOC e1649Fwu struck a chord with mobile professionals because they lent themselves well to working from off-site locations such as hotel rooms. Now AOC is going bigger with the $199 e2251Fwu, a 22-inch external monitor that not only is the largest USB-powered display out there but also ups the resolution to a tack-sharp 1920 x 1080. That's a load of pixels and real estate for a USB port to power.
Design and Portability
Click to EnlargeAt 19.9 x 12.3 x 0.4 inches, the oil-black monitor is quite slim. It's not as clunky as AOC's bubbly 15.6-inch e1649Fwu, but the front bezel is made of cheap, glossy plastic. The back actually looks better because it uses matte plastic with an etched diamond-shape mosaic pattern. This treatment also makes the screen easier to grip when carrying.
Also around back is a large bump that houses the USB port. There's a power adapter jack, too, but that component is sold separately since the monitor works entirely via USB power. Jutting out beneath those ports is a stubby but sturdy stand. Unfortunately the support isn't adjustable, so you can't tweak the monitor's angle. AOC includes an alternative stand that raises the monitor 5 inches in the air, but you can't tilt or adjust that support, either.
The last piece to the e2251Fwu is a cord with a single male USB port on one end and two male USB heads on the other. The single end connects to the monitor, and the dual end goes into your PC. Though there are two USB jacks on one end of the cord, most computers require only one USB port to be plugged in for the monitor to work.
You can certainly carry the e2251Fwu with you--it weighs just 5.2 pounds--but do you want to? The monitor won't fit in any notebook bag, and it's too big for most backpacks, plus there's no way to protect the screen when it's tucked away in something larger, such as a suitcase.
The e2251Fwu supports plug-and-play connectivity for both Windows and Mac OS X laptops and desktops. Once we connected the USB cord to a Dell XPS 13, the monitor was up and running after just a few screen flickers. The same goes for a 13-inch MacBook Air. If plug-and-play fails, AOC includes an installation disk with drivers, or you can download the drivers from Displaylink.com.
Monitor-management software accessible via the taskbar let us mirror the display, duplicate it, change screen orientation, even rearrange the two screens' relation to each other. Of course, adjusting display settings via the Control Panel (Windows) or in Monitor Settings (Mac OS X) worked, too.
Image Quality and Performance
Click to EnlargeA 22-inch LED-backlit monitor with a 1980 x 1080 pixel resolution that relies solely on a single USB port for power has the potential for poor image quality, but what the e2251Fwu offered was beautiful. We spotted all sorts of detail in a downloaded 1080p trailer for "Skyfall," including the outline of a city skyline reflected in the facade of a skyscraper and the crispness of the Union Jack covering soldiers' coffins.
With an average brightness of 207 lux, the e2251Fwu is the brightest USB-powered monitor we've tested, outshining smaller displays such as the 14-inch Lenovo ThinkVision LT1421 (111 lux) and the 16-inch AOC e1649Fwu (148 lux). Plus, thanks to the matte finish, viewing angles were wide enough for a small group of people to see the screen comfortably. AOC markets the e2251Fwu as a presentation tool for business users; images in a sample PowerPoint slide looked sharp even from a few feet away.
In fact, the only time we noted poor image quality was when the e2251Fwu was plugged into its optional base stand. Although the stand elevates the display by about 5 inches, it also tilts the monitor forward at an angle that made the display appear several shades darker, even when viewed at eye level. The problem wouldn't exist if the screen tilted backward a touch, but the e2251Fwu can't be adjusted unless you physically slide the display.
While connected to a Dell XPS 13 ultrabook with an Intel Core i5-2467M processor, the e2251Fwu used between 14 percent and 20 percent of the CPU's power. Performance levels were the same in a Dell Inspiron notebook with a less powerful Core i3 processor. We noticed brief spikes up to 24 percent when we watched the 1080p "SkyFall" trailer at full screen on both systems, but that's not much, considering a visit to YouTube in Google Chrome provided a short burst to 30 percent CPU usage. That means the e2251Fwu isn't a resource hog.
The $199 AOC e2251Fwu Monitor delivers bright, detailed video and images (as long as you avoid using the optional base stand) without requiring AC power. And thanks to the matte display, the monitor's viewing angles are comfortably wide for presentations and movies. However, while the freedom to leave the AC adapter at home makes this device more portable than traditional 22-inch monitors, the AOC's size doesn't lend itself to travel.
If you want a spare display for the road, we prefer the lighter 14-inch Lenovo ThinkPad LT1421. Although it has a lower resolution (1366 x 768), the monitor fits in a bag for the same $199 price. But if you're willing to lug around more weight and want maximum detail, the AOC e2251Fwu is certainly worth a look.