Anaglyph 3D

Anaglyph 3D is the stereoscopic 3D effect achieved by encoding each eye's image using filters of different, usually chromatically opposite, colors, typically red and cyan. Anaglyph 3D images contain two differently filtered colored images, one intended for each eye. When viewed through color-coded anaglyph glasses, each image is visible only to the eye it is intended for, revealing an integrated stereoscopic image. The visual cortex of the brain fuses those images into the perception of a three-dimensional scene or composition.

Anaglyph images have seen a recent resurgence due to the prevalence of images and video on the Web, on Blu-ray, CDs, and even in print. Low cost paper frames or plastic-framed glasses hold accurate color filters that typically, after 2002, make use of all three primary colors. Although most common color filters used today are red and cyan, with red being used for the left channel and vice versa, the filters used in the past used red and blue for convenience and cost. There is a significant improvement in the reproduction of full color images using the cyan filter, especially for accurate skin tones.

Video games, theatrical films, and DVDs can be shown using the anaglyph 3D process. Practical images, for science or design, where depth perception is useful, include the presentation of full scale and microscopic stereographic images. Examples from NASA include Mars rover imaging and the solar mission STEREO, which uses two orbital vehicles to obtain three-dimensional images of the sun. Other applications include geological illustrations by the United States Geological Survey, and various online museum objects. A recent application is stereo imaging of the heart using 3D ultrasound with plastic red/cyan glasses.

Anaglyph images are much easier to view than either parallel (diverging) or crossed-view stereograms. However, these side-by-side types offer bright and accurate color rendering, which is not easily achieved with anaglyphs. Also, extended use of the anaglyph glasses can cause discomfort, and the afterimage caused by the colors of the glasses may temporarily affect the viewer's visual perception of real-life objects. In the mid-2000s, cross-view prismatic glasses with adjustable masking have appeared, offering a wider image on modern HD video and computer monitors.