ref:
http://www.retrevo.com/content/blog/2010/11/should-you-wait-passive-3dtvs?cmpid=EmailB
Oakley, the company best known for high quality sunglasses was in the news recently with an announcement of their new circular polarized “passive” 3D glasses called 3D Gascans. These glasses can be used to watch movies that use the RealD (polarized) format which is currently only available in movie theaters. However, soon you might be able to use these and other "passive" glasses to watch 3DTV at home when 3DTVs that feature passive 3D technology become available from companies like Vizio and LG.
3D Glasses Format War?
Just when we thought everyone was going to play nice and move forward with one standard for 3DTV glasses in the home, we start to see a division growing between LG and Samsung the two largest LCD panel manufacturers in the world. Samsung, Sony and others have settled on active shutter glasses while LG and Vizio are about to introduce 3DTVs that use passive glasses. Nvidia, which offers 3D technology for things like 3D computer gaming has also indicated a preference for active shutter glasses.
Is There A Difference in the 3D Experience?
Active shutter glasses use an IR beam from the TV to synchronize LCD shutters in the glasses which trick the brain into thinking it’s seeing one 3D image from two alternating frames. Passive glasses, like the ones from RealD that are commonly used in movie theaters use circular polarizing filters to send different images to each eye. Dolby 3D glasses, also commonly used in theaters use a different "passive" technique. Active glasses require batteries and typically cost over $100 a pair. Passive glasses are much cheaper, lighter and don’t require batteries.
Passive 3DTV sets like those coming from Vizio and LG require a micro-polarizing filter precisely embedded in the screen so the TV can send every other line of the 1080 lines to each eye. Because of this each eye only gets 540 lines or half the pixels of a full, 1080 frame. The added polarizer filter could also add cost to the TV, at least, at first.
Most distributors of 3D programming like cable and satellite companies take a full 1920 x 1080 (HD) resolution feed and use one of several techniques to reduce the bandwidth requirements which allows them to use existing bandwidth to distribute 3D programming.
Two common techniques are side-by-side that removes half the horizontal pixels leaving 960 pixels per frame and over-under that removes half the vertical lines resulting in 540 lines for each eye. Typically, 3DTVs using active shutter glasses take the half-resolution frames, add the missing pixels through a technique like interpolation and display alternating, full HD resolution frames at high frame rates. Passive TVs will add the missing horizontal pixels if necessary but will still show only half the vertical pixels.
Whenever you remove half the pixels that originally came from the 3D camera you're going to lose some image quality even though you do get some of those pixels back through pixel-adding interpolation. Blu-ray distributed 3D material delivers the most 3D pixels but even with passive 3DTVs you're still going to lose half the vertical resolution from a 3D Blu-ray movie because it's only going to show 540 lines to each eye. To be fair, some experts maintain that your brain will compensate for the missing pixels and you'll never notice any difference. On the other hand, when you sacrifice 50% of the pixels, brightness may be reduced. Fortunately LCD TVs can generate a lot of light to compensate for some of that loss.
Cost, Interoperability and Practicality
Despite the fact that Oakley is charging over $100 for their Gascan glasses, passive glasses will most likely cost well below $50. You should even be able to put them in a dishwasher just like the movie theaters. Cheaper glasses mean less cost to equip a family or group of viewers and it would be much less costly when someone accidentally sits on a pair of them which you know is going to happen to you 3D glasses sooner or later. The other advantage is they should all work with any RealD-powered 3DTV set or movie theater. The trade off may be in a higher priced passive 3DTV set however, maybe Vizio (known for competitively-priced TVs) can deliver a low priced, passive set out of the gate.
Interoperability has been an issue with active shutter glasses. There is no standard that manufacturers have agreed on that would make one pair of active shutter glasses work with any active shutter TV. The Consumer Electronics Association (CEA) has said they are addressing this issue and hope to have a standard in place before too long. Meanwhile a company named XPAND announced its Universal X103 3D glasses ($129 on Amazon) that can work with a long list of 3DTVs.
Bottom Line
We haven't seen passive 3DTV with our own eyes but we are curious to see how the half resolution of 3D images compare to the full resolution possible with active shutter (from a full 3D HD source). Needless to say passive glasses have a lot of practical advantages over active shutter glasses but it remains to be seen which ones offer the superior experience. We'll also be watching to see if Dolby's passive technology makes it into 3DTV sets any time soon. Dolby could represent a third standard for 3D glasses in the home.
No comments:
Post a Comment