Passive Aggressive 3D

The daily deluge of news into my inbox included a very sad item yesterday. Insight Media, a display-industry analysis firm, reported that Samsung will not be making so-called "active retarder" 3D LCD TVs in collaboration with RealD. This approach places an active polarization-switching layer over the LCD layer, much like the polarization switcher placed in front of a projector lens in a commercial RealD theater. The viewer wears standard passive glasses, and the TV quickly alternates the polarization in sync with the alternating left and right images on the screen.

Prototypes were demonstrated at CES last January and at the Society for Information Display (SID) convention in May (shown above); see my blog about that demo here. Since I became aware of it, I've thought this technology provides the best of both worlds—the brighter image, absence of crosstalk and flicker, and lightweight, inexpensive glasses of passive 3D with the full resolution of active 3D.

So why did active-retarder technology stall before it even left the starting gate? I'm sure one factor is expense—with an extra active screen layer, such sets must cost more to make. Of course, this adds to the retail price tag at a time when most consumers are looking for less-expensive TVs. Then there's the apparent waning of consumer interest in 3D with the rise of online streaming, though both appeared at roughly the same time and are now simply features of most midline and high-end sets.

Perhaps another factor is the growing number of less-expensive, fully passive 3D TVs from LG, Toshiba, and Vizio. These sets use a layer called a film patterned retarder (FPR) that alternately polarizes each line of the image—all the odd-numbered lines are polarized one way and all the even-numbered lines are polarized the other way, and passive glasses isolate each set of lines for the appropriate eye.

You might think this means each eye sees only 540 lives of vertical resolution, and you'd be right in one sense, but not in another. As I explain here, LG claims that each eye actually sees all 1080 lines of resolution on its passive-3D screens—just not all at the same time or in precisely the same location. According to video guru Joe Kane, this results in visible artifacts as I report here, based on test patterns he has created.

Adding fuel to the fire is a recent study conducted by DisplayMate Technologies, a display calibration and evaluation company. After comparing two FPR passive 3D TVs with two sets that use active-shutter glasses, the findings of this exhaustive study, which can be found here, clearly indicate that viewers do see 1080 lines of vertical resolution in FPR 3D images due to a psychophysical phenomenon called image fusion. In this process, the brain fuses the left and right images into a single, 1080p 3D image when you are farther than a certain distance from the screen, based on human visual acuity—for example, about 6 feet from a 47-inch TV.

Even more amazingly, the study found that small details were actually sharper on the FPR TVs than they were on the active-glasses models. The report concludes that this is due to greater crosstalk/ghosting and response-time issues endemic to active-shutter glasses.

As expected, the FPR images were also brighter, exhibited less crosstalk/ghosting and no flickering, and caused less discomfort in most viewers. However, the report acknowledges that, while the horizontal viewing angle is wider on FPR sets, the vertical viewing angle is narrower than for active-glasses displays. This means you can't watch an FPR TV while lying on the floor without lots of crosstalk/ghosting, unless the set is angled downward so your line of sight is perpendicular to the screen.

In my own experience, I've been surprised that the sharpness of 3D images on FPR sets is far greater than I would have expected. However, I do tend to see very thin black horizontal lines that presumably separate the left and right images, even at the correct distance from the screen. (The DisplayMate report claims these lines disappear beyond a certain distance, but I still see them.)

FPR images are certainly brighter with little or no crosstalk/ghosting. And passive glasses are way more comfortable to wear, especially over my prescription glasses, for extended periods—not to mention they are way less expensive than active-shutter glasses, and you can use them in RealD commercial theaters. As for the flicker effect reported by many viewers with active-shutter glasses, I've never seen it, so that must be an individual-sensitivity thing, like the rainbow effect with single-chip DLP displays.

Despite Joe Kane's demonstrations with test patterns, the bottom line is, how does real-world content look? Aside from those thin black lines, it looks great to me, and I'm not alone. When I showed a non-industry friend some 3D on the 65-inch Vizio XVT3D650SV FPR set (reviewed here), he said it was the best 3D he'd ever seen.

I look forward to reviewing more FPR 3D TVs, and perhaps conducting a face-off of my own between FPR and active-shutter technology. Meanwhile, I mourn the demise of active-retarder technology, which truly was the best of both worlds.