Broadcast Engineering on 3D

Consumer Reports examines passive 3-D set from Vizio

At last month’s CES, LG, Toshiba and Vizio announced passive 3-D TVs that allow the user to wear lightweight, inexpensive polarized glasses like the ones used in movie theaters. The polarized glasses are not only much cheaper, but replace the bulkier active-shutter glasses required by most current 3-D sets.

The first passive 3-D TV to hit the market was Vizio’s 65in VT3D650SV, a 1080p LCD TV that uses an edge LED backlight. Consumer Reports recently tested the Vizio model, pitting it against the Panasonic TC-P65VT25, a top-rated plasma 3-D TV.

In general, Consumer Reports said, there is a lot to like about the VT3D650SV. For one thing, the research team found the polarized glasses very comfortable to wear. The team also noted that consumers get four pairs of glasses with the TV, with additional pairs expected to cost from $10 to $30. That’s much cheaper than the $130 to $150 active glasses cost.

In addition, the test team said the passive 3-D glasses dim the image less than any of the active-shutter glasses they had tried, enabling the Vizio to produce the most satisfyingly bright picture experienced so far when viewing 3-D TV. Perhaps even more important, Consumer Reports said, ghosting, which has been a significant distraction on almost all the 3-D LCD TVs so far reviewed, is reduced to the point where it gives plasma TVs a run for their money.

However, the test team said the significant downside to the passive 3-D technology is the noticeable loss of resolution that’s the result of the way the separate 3-D images are displayed for each eye.

Passive TVs use a different technology than the current active 3-D sets already on the market. Unlike those sets, which use active glasses with shutters that rapidly open and close to provide each eye its own view, passive TVs use a polarizing film on the TV screen itself, which divides the picture into alternating lines. Each lens in the glasses blocks the images meant for the other eye.

As a result, each eye only receives half the vertical resolution of the image. So while active sets can send full-HD 1080p (1920 x 1080) signals to each eye when connected to an HD 3-D source, such as a 3-D Blu-ray player, the best a passive 3-D TV can do is 1920 x 540.

If one gets 3-D signals via cable or satellite broadcasts, which squeeze 3-D signals into the space meant for a single HD image, cutting the horizontal resolution, the resolution is reduced even further, to 960 x 540. This loss of resolution may be visually subtle to some viewers, depending on the 3-D program material, but it’s likely to be noticeable and bothersome to more discerning viewers.

In the Consumer Reports test, this loss of resolution resulted in interlaced-like image effects, such as jaggies and moiré, which recall 480i TVs. For example, overall picture detail was much courser on the Vizio than with the Panasonic, and there was visible blurring on objects in motion in some scenes.

In addition, the test team saw jaggies on the edges of objects, especially on diagonal lines. When comparing a detailed, 1080p 3-D freeze-frame Blu-ray image on the Vizio and Panasonic sets, the difference is quite apparent. Depending on the scene, the Vizio often exhibited significant jaggies and moiré; images on the Panasonic were detailed, smooth, filmlike and free of classic video artifacts.

At CES, Consumer Reports said it appeared that passive 3-D was being positioned as 3-D for the masses, while active 3-D was targeting enthusiasts more concerned with absolute picture quality.

“Based on our preliminary tests, we see no reason to alter that assessment,” the Consumer Reports team said.

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