IMAX is known for going big when it comes to cinema -- really, really big. IMAX also makes no secret of its 3D offerings, which combine the literally eye-popping magic of 3D with the massive IMAX image. There's quite a big difference between IMAX 3D and the 3D effect you can get from most high-end HDTVs.
One of the key differences between IMAX 3D and 3D in general is the technology at play. IMAX utilizes a polarized lens system, where two images are superimposed slightly off center from one another on the screen using projectors with polarized filters. The polarized lenses in the glasses match the filters on the projectors and filter the incoming light, and the resulting image gives the viewer the illusion of depth.
Polarization is just one of several available technologies that produce similar depth illusions. Anaglyphic 3D uses a similar principle, replacing polarized light with color-filtered images. You might recognize anaglyphic glasses as the stereotypical red and blue cardboard 3D glasses of pop culture. Active-shutter 3D takes the concept in a mechanical direction, projecting two slightly off-center images on the screen which alternate at imperceptibly high speeds. The glasses contain shutters synced to the projections, opening only one eye to the image at a time at the same high speed. This creates another illusion of depth. Another technology is autostereoscopic 3D, which requires no glasses at all. Instead, images are set up with the viewing field of each eye in mind and carefully aligned to trick the eyes into creating the illusion of depth.
One of the most obvious differences is the sheer scale. IMAX is well-known for its dauntingly big screens. As of the time of publication, the largest in the world measures a massive 96.5 feet high. When viewing 3D in this scale, effects take on a whole new level of impact compared to a smaller resolution experience in the home or even conventional theatres.
Active vs. Passive 3D
Most forms of 3D, including the polarization system utilized by IMAX, are considered "passive 3D." The exception is the aforementioned active-shutter 3D. Passive 3D systems like IMAX actually cut the overall image resolution in half, dividing that resolution between the two eyes. Active 3D systems use full resolution images.
Glasses Vs. Glasses-Free
Most forms of 3D also require audience members to wear specialized glasses, and IMAX is no exception. However, autostereoscopic 3D can also provide a glasses-free experience. Popular examples of stereoscopic 3D include the Magic Eye series of visual puzzles and Nintendo's 3DS handheld gaming system.
Another key difference is the sound system. IMAX utilizes a massive array of speakers, both outside of the screen and behind it, to deliver an overwhelming surround sound experience. With other 3D technologies, sound may not be a component of the show simply because not every film displayed in 3D may be equipped for it. The sound and its integration into the 3D experience always varies based on the theatre it's presented in, while IMAX is consistent about incorporating big sound with its big picture.
Another key difference is the film lineup offered by IMAX 3D. While many feature films with 3D effects are shown on IMAX 3D, there are also a number of unique films produced by the IMAX company specifically for viewing on their IMAX 3D system utilizing specialized camera equipment.