Price: $2,300 At A Glance: Outstanding black level and shadow detail • 240-hertz-like operation • Full range of calibration controls

An LED Touchdown

LCD HDTVs have long been compromised in their ability to reproduce the deepest blacks together with good shadow detail. But that’s changing. We’ve seen some notable improvements in a few recent conventional sets. However, the change has been most pronounced in sets that use a revolutionary new development: LED backlighting with local dimming.

Until now, LED backlighting, particularly when combined with local dimming, has been a complex design technique only used in a few very expensive sets (some sets offer LED backlighting without local dimming). Toshiba now shatters that price barrier with the $2,300, 46-inch 46SV670U. (Toshiba also offers a 55-inch version, the 55SV670U, at $3,000.) While 23 big ones isn’t exactly in blue-light special territory, it’s thousands less than what much of the competition demands.

Each pixel in an LCD set acts as a gate, either emitting or blocking light based on the source’s requirements. But an LCD isn’t self-illuminating; the light it passes or blocks must come from a backlight that’s located behind the LCD panel. Traditionally, this backlight is a grouping of fluorescent tubes. Once it’s adjusted by the backlight control, the illumination remains fixed.

Unfortunately, the inherent light-blocking ability of LCD pixels isn’t perfect. Some of the illumination from the backlight can still pass through them, even when the source calls for total black.

But replacing the fluorescent backlight with dozens (or hundreds) of clusters of colored (or color-filtered) LEDs offers a new possibility. By controlling the brightness of the LEDs or even shutting them down completely if the image calls for it, you can supplement the limited light-controlling capabilities of the LCD pixels by reducing the amount of light they must block. Even better, it’s possible to arrange the LEDs in hundreds of zones behind the screen and lighten or darken each zone separately. In effect, the LED backlights provide a source-dependent, appropriate degree of brightening or dimming in different regions of the screen. At the same time, the LCDs block the light as required to render the picture at the pixel level. The two types of devices work together to produce a highly detailed image and deep, rich blacks.

Inside Story
The Toshiba 46SV670U offers a full range of inputs on its side and rear jack panels. These include four HDMI inputs, two component video inputs (Toshiba calls the latter ColorStream HD), and a USB port to play back photos, music, and movies that are stored on USB devices. It also has an SD card slot for viewing photos and a PC connection. But it doesn’t have an Ethernet (LAN) terminal.

This set has six preset picture modes. The picture controls in each of them are individually user-adjustable (with some limitations). You can also set up the controls differently for each picture mode when you use it on more than one input (again with some exceptions). I chose the Movie mode for all of my viewing, with appropriate control adjustments.

Most of the interesting video controls are located in the Advanced Picture Settings menu. Toshiba refers to its LED local dimming feature as FocaLight in its literature and the list of features at the front of the owner’s manual. Oddly, the same feature is called DynaLight in both the manual’s operating instructions and the Advanced menu.

When you turn DynaLight off, the LED backlighting remains on, but it’s in a fixed mode with no local dimming. This significantly degrades the set’s black level. The DynaLight control you’ll see on other Toshiba sets—sets without local dimming—doesn’t perform the same functions or offer the same benefits as it does here.

Other Advanced Picture controls include Color Temperature and ColorMaster. Color Temperature includes fixed settings plus separate white-balance calibration adjustments (high and low, red, green, and blue). ColorMaster, Toshiba’s name for its color management system, provides hue, saturation, and brightness control for both the primary (red, green, blue) and secondary (yellow, magenta, cyan) colors.

A so-called Expert mode lets you turn on only the red, green, or blue portion of the signal. This feature, together with an appropriate color bar pattern, is the best way to accurately set the color and tint. People often use color filters for this purpose, but these filters aren’t always accurate, particularly with LCD sets.

Resolution+ is a feature that’s designed to help SD material look a bit more like HD. Its most visible effect was the addition of edge enhancement. I left it off.

The Advanced picture settings also include Static Gamma and Dynamic Contrast. Roughly stated, Static Gamma controls the light output in the mid-brightness range. I found that a setting from –1 to –3 worked best, depending on the source.

Dynamic Contrast punches up the image. While it’s tolerable at low settings and might help in a very bright room, I found the result to be unnatural looking. For serious viewing, I left it at 0.

According to Toshiba, the auto brightness sensor “automatically optimizes the backlighting levels to suit ambient lighting conditions.” Related to this is the Backlight Adjustment Pro control, which adjusts how aggressively the auto brightness sensor does its job. For me, these types of auto functions only degrade the accuracy of the picture. I left them both off.

Is 240 Hertz Faster Than 120 Hertz?
Most LCD manufacturers have incorporated a 120-Hz refresh rate in their newest sets. When combined with processing that adds interpolated frames to the program material’s real frames, this feature can greatly smooth motion and reduce motion blur, which is a persistent problem with LCD displays. Some sets even up the ante to 240 Hz, which claims to produce further advantages.

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