Anaglyphs are images which have a three dimensional effect when they are viewed through filtering glasses or lenses. Many people are familiar with the concept of an anaglyph although they may not be familiar with the term, because this technology is the basis of most 3-D movies. Anaglyphs can be moving or still images, and they can vary in quality depending on a number of factors including how they were produced and processed. Many image and video editing programs have the capacity to make anaglyphs.
In an anaglyph, there are offset color layers. Viewed without special lenses, the image appears blurry and ghosted and can be hard to discern. When glasses with colored lenses are worn, each eye sees a slightly different version of the image, and the brain merges the incoming visual information and creates the illusion of a three dimensional experience. Some things in the image will appear to pop out, while others will recede.
The anaglyph takes advantage of certain traits of visual perception, tricking the eyes and the brain into thinking that they are seeing something in three dimensions instead of two. One advantage to using anaglyphs for 3-D effects is that they do not require any effort on the part of the viewer, while images which do not require glasses actually require some practice to view. The glasses used can also be produced very cheaply, making it practical to distribute them to viewers so that they can see the illusion.
One way to produce an anaglyph is to take two shots from slightly different perspectives and merge them. This tends to create more depth and texture in the finished image, and it can allow for greater manipulation of the distance between the layers to address issues such as ghosting, which sometimes occur when one eye catches sight of something intended for the other eye. Anaglyphs for commercial use are often made this way because the image quality can be higher.
It is also possible to process a flat image to turn it into an anaglyph. In this case, an image processing program separates out the layers for the user and allows for some manipulation to achieve the desired effect. Someone who is skilled can often produce a very good anaglyph image using processing techniques, although it does take some practice. This process can be painstaking when it comes to converting video, as each frame must be treated separately.