Just days before the kickoff of the annual Consumer Electronics Show (CES), it's already clear that the debut of new "passive" 3D TVs will be among one of the show's highlights. These new LCD TVs, already announced by Vizio and LG Electronics, use lightweight, inexpensive polarized 3D glasses, like the ones you get in most movie theaters, instead of the bulkier and costlier active-shutter glasses required by the current crop of 3D TVs.
Passive 3D TVs are constructed a bit differently than active models, primarily in their use of a polarized film to separate the left- and right-eye images. Where active glasses have shutters that open and close rapidly to give each eye a separate image, passive glasses use polarization to block out images that aren't meant for that eye. While polarized glasses are much less expensive to make than active-shutter models—we expect to see polarized glasses priced between $15 and $30 each, compared to $130 to $150 for a pair of active glasses—passive TVs have typically cost much more to manufacture. So while the glasses are cheap, the TVs have tended to be expensive.
But based on Vizio's pricing for its new models—its 65-inch set will sell for about $3,700—it seems that passive TVs won't cost much more than active 3D sets. (LG hasn't yet announced pricing for its passive sets.) One reason is that manufacturing procedures have improved. Another is that these TVs can use 120Hz frame rates, where almost all the active 3D sets we've seen have 240Hz or 480Hz technology. And another benefit of passive is that because they don't use glasses with shutters, they should be relatively free from flicker. And manufacturers claim there is less crosstalk, a problem that's plagued all the LCD 3D TVs we've tested so far.
So if passive 3D TVs are competitively priced with active models, and the 3D glasses are significantly cheaper, then it won't be long until the market for 3D shifts almost exclusively to passive. Right?
Well, not exactly. The fly in the passive-TV ointment is that due to the way that the polarizers work, the vertical resolution of passive 3Ds is cut in half when viewing 3D content. So instead of the 1080p (1920 by 1080) being sent to each eye in an active set, the resolution of a passive 3D TV is 1920 by 540. (The TVs have full 1080p resolution when viewing regular high-def TV programs and Blu-ray movies.) Also, the vertical viewing angle has been fairly restricted in the passive 3D TVs I've seen previously, so there's a question as to whether these newer models will have a similar issue and whether it will be off-putting for viewers.
Consumer Reports has already ordered one of Vizio's new passive TVs, but until we have a chance to evaluate it, we can't say whether the loss of resolution is meaningful. Also, we've been told that LCD TVs will have less crosstalk than active LCD models, so perhaps the tradeoff will be acceptable to many consumers. But Claudio Ciacci, our head TV engineer, had an interesting question that so far no manufacturers have been able to answer: "Since the horizontal resolution of broadcast 3D TV, such as that being provided by DirecTV, Dish, Verizon, and cable operators, has already been cut in half due to the side-by-side format being used, does that mean that these shows will have only one-quarter resolution (960 by 540) when viewed on a passive 3D TV?"
During CES, we'll be visiting the exhibits of all the companies planning to offer passive 3D TVs to offer our first impressions, so keep checking back with our blog for complete CES updates. And of course, we'll let you know when we've completed our comprehensive testing of these sets in the CR TV Test Labs.
—James K. Willcox