The Renaissance of 3D:
How the New 3D Technologies Work
"Anaglyph" is a fancy word used to describe the most basic style of 3D projection in use. The left- and right-eye images are superimposed (usually recorded onto the same film stock) and color differences are used to separate the two. The viewer wears a pair of colored-lens glasses (traditionally red and cyan) which force the eyes to differentiate between the two. The end result is the impression of depth. The anaglyph method is primarily used for home releases of theatrical movies--even if those movies did not use anaglyph in the cinema--because it is inexpensive and easy to use. Until now, if you have seen a DVD or Blu-ray labeled "3D," it uses the anaglyph method.
Advantages of Anaglyph 3D
Accessible. The anaglyph method is used for current 3D DVDs and Blu-ray discs because it requires no special equipment. You don't need a "3D-ready" projector or television. It will work on your current television or projector regardless of technology, frame rate, aspect ratio, resolution, or anything else. If you can watch a movie, you can watch an anaglyph movie in 3D.
Inexpensive. The DVD and Blu-ray discs in anaglyph 3D typically cost no more than their 2D counterparts and include four pairs of cheap cardboard-framed glasses. Since there is no extra expense to the consumer in glasses, video displays, or DVD players, it is by far the least expensive 3D system out there.
Passive Technology. We will discuss this in more depth shortly, but anaglyph 3D uses passive glasses. Passive glasses have no circuitry or electronic parts which makes them inexpensive, easy to use, and lightweight. This is ideal for children and larger audiences as instances of glasses breaking or "walking away" do not cause significant financial hardship.
Disadvantages of Anaglyph 3D
Color. The big problem with anaglyph 3D and one of the reasons people have a poor impression of 3D overall is poor color. When one lens is tinting everything red and the other is tinting everything cyan, color can seem a little out-of-whack. These days post-production houses are able to adjust the color such that it looks more normal, but everything still takes on a sort of shimmery look and colors don't seem as solid or definitive as they do in normal 2D.
Light loss. A filter by definition removes things which are unwanted or undesirable. For an anaglyph system to work only selected wavelengths of light are allowed to reach the viewer's eyes, so all other wavelengths are undesirable. As a result the image seen through anaglyph glasses is much dimmer than a comparable 2D image.
Cross-talk. Partly due to the design of the glasses and partly due to the use of color filtering, anaglyph 3D is more prone to cross-talk than other technologies. Cross-talk occurs when one eye sees a portion of the image meant for the other eye. It is distracting and obvious when it occurs and it breaks the viewer's immersion in the material.
Eyestrain. Anaglyph also tends to cause more eyestrain than other technologies. Some attribute this to the use of red and cyan filters which change the wavelength of light entering the eye. Cheap glasses do not have the ability to correct for this. As a result, one eye's focal distance is different than the other's and the eyes can have a hard time focusing. Coupled with the effect of 3D video, which is already taxing to the eyes, anaglyph can give some people eyestrain-induced headaches.
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