In the “old days” of 3D movies, commercial theaters employed what are called “anaglyph” 3D glasses. Using a different colored lens (one red, one cyan) for each eye, anaglyph 3D glasses utilized color filtration to determine which eye saw which image sequence. Funneling these offset images separately into each eye via anaglyphic color filtration worked to an extent, although the effect was somewhat primitive and unreliable. The biggest compromise resulted from the fact that the lenses had to be colored, which reduces the color quality of what you’re watching. Nevertheless, it was a beginning.
Circularly-polarized lenses are what modern passive 3D glasses use to provide the 3D effect. Not unlike how stereo recording is done with two mics positioned a short distance apart, two cameras are used during the filming process, and both image sequences are replayed simulataneously. In the case of passive polarized 3D technology, however, the left and right lenses of your 3D glasses are polarized differently, thereby only allowing one image sequence into your left eye, and a different one into your right eye. So, like the spacing of your eyes produces the 3D depth you see in real-life, having separate, offset images going into each eye simulates real 3D.
Commercial three D projectors are utilized by commercial cinemas and take advantage of circularly polarized light so that you don;t have to keep your head perfectly straight to see the 3-D effect. These projectors also save on costs since they can alternatively generate right circularly polarized and left circularly polarized images in rapid succession without the need for two independent projectors.
Consequently, when you are at the theater, you can tilt your head and still percieve the 3D effect in an undistorted fashion. And, just as it is in the cinema, current models of passive polarized 3D HDTVs also employ circular polarization so that head angle is irrelevant in your home, too. One TV that utilizes circular polarization technology is the LG 55LW6500.
You might wonder, then, what are the strengths and weaknesses of passive polarized 3D lenses?
Pros:
-> No “ghosting” or image bleedover between eyes.
-> Completely flicker-free, which is not always the case with active shutter 3D glasses.
-> Unlike anaglyphic lenses, the color is outstanding.
-> Low enough in cost that you can afford to buy extras for friends, family, and guests. -> The same technology movie theatres employ, which means the glasses you got ta the theatre will likely work on your set at home.
-> Small and light, which makes wearing them to watch more pleasant.
Cons:
-> Previously, projection televisions worked better with it since light polarization can degrade when passing through a screen. The reason for this was that when light passes through the screen from within the television, it sometimes didn’t properly retain its polarization. Regardless, modern 3D HDTVs have solved this problem.
-> If you were to opt for a projection system, you would be looking at a significantly greater expense. Though, as mentioned, this is really no longer necessary. Still, hard-core enthusiasts will likely be happy to spend the extra money for the higher-quality projection set.
-> Some users argue that the 3D experience with active shutter 3D TVs is better, although others disagree.
All in all, active shutter glasses, while some have said they’re better, have a few disadvantages when compared with passive polarized 3D glasses. Chief among the advantages is that passive polarized glasses are easier to wear. Particularly since there are now low-priced sets like the LG 42PW350, you will certainly be pleased if you choose a passive polarized 3D TV.
