|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.