Vizio VF551XVT LCD HDTV
LED for the Masses
At the 2009 CES, Vizio took the wraps off of its first LCD HDTV with LED backlighting and local dimming, which consumers have been eagerly waiting for ever since. At $2,200, the VF551XVT is the least expensive 55-inch local-dimming LCD available, which makes it mighty attractive to cash-strapped TV shoppers. How well does it fulfill the promise of LED backlighting? Read on to find out...
When the VF551XVT was unveiled at CES in January 2009, the soundbar below the screen was bright red, which I complained about at the time. In the production version, it’s bright silver, which isn’t any better. I really wish Vizio had gone with black, which would be far less distracting.
The most important feature is LED backlighting with local dimming. If you’re unfamiliar with this feature, the backlight behind the LCD imaging panel is composed of many white LEDs rather than fluorescent lights as in conventional LCD TVs. (A few such TVs use red, green, and blue LEDs, but like most manufacturers, Vizio uses white ones.) The LEDs are combined into groups or zones, each of which can independently dim or brighten behind different sections of the image. In essence, the LEDs form a very low-resolution version of the high-resolution image in the LCD panel.
For example, if the onscreen image has a bright object on a dark background, the LEDs behind the object brighten while the LEDs behind the dark areas dim. This results in much greater contrast and deeper blacks than fluorescent backlights can manage. Most fluorescent backlights can change their brightness according to the overall brightness of the image, but this affects the entire screen.
Local dimming does have some drawbacks. Chief among them is the fact that there are only a couple thousand LEDs grouped into about 100 zones. (These are only rough estimates; most manufacturers don’t reveal the number of LEDs and zones they use.) When you consider that there are more than 2 million pixels in an LCD panel, it’s clear that the backlight can’t match the resolution of the picture itself. As a result, some types of images, such as white credits over a black background, can exhibit halos around the bright objects.
Another feature that Vizio touts is 240-hertz operation. However, in this case, the TV flashes frames on the screen 120 times per second, and the backlight pulses on and off in a particular pattern to simulate a refresh rate of 240 Hz. In conjunction with Vizio’s frame-interpolation algorithm, this is designed to reduce the motion blur that has plagued LCD HDTVs since their introduction. It also reduces the judder—a slight herky-jerky quality in any onscreen movement—that is often associated with film-based video sources.
Frame interpolation creates new frames and inserts them between the actual frames in a video signal. It calculates where moving objects should be in those new frames to smooth out the motion and sharpen the image. However, this process can introduce artifacts of its own.
The VF551XVT provides two controls—Smooth Motion and Real Cinema—that determine the amount and type of interpolation, respectively. It lets you balance the increased sharpness with any artifacts that might intrude.
In addition, frame interpolation gives the image a video-like look, which some viewers hate. I’m not one of them. Of course, I recognize it, but it doesn’t bother me nearly as much as blurry objects in motion. For viewers who find this intolerable, you can always disable it.
A side-mounted USB port lets you attach a storage device and play many different types of stored media files. Video-wise, the VF551XVT can play H.264/AVC, MPEG-4 ASP, MPEG-2, and several forms of WMV, including VC-1. The TV can support resolutions up to 1920 by 1080 in all of these formats except MPEG-4 ASP, which is limited to 1280 by 720. The audio that accompanies the video can be AAC, WMA-7/8, or AC3 (Dolby Digital), depending on the video format. The Vizio can also play MP3 audio files and display JPEG photos from the USB device.