Anaglyph 3D refers to layered images that produce an optical 3D effect when viewed through red-cyan glasses. The left lens of these glasses is red and the right lens is cyan, which means that the left eye and right eye each view the layered image in different colors. The red filter allows the left eye to see only the red part of the anaglyph image, rendering the green and blue portions dark, and the cyan filter allows the right eye to see only the green or blue portions, rendering the red parts dark.
The brain is tricked by the color difference into considering the image as being two separate images, and it combines them to form an anaglyph 3D image. The actual image itself is composed in a particular way to make the visual illusion possible. It consists of two superimposed images that are offset to a certain degree to create the perception of depth. Usually, the main subject is positioned at the center and the background elements and the foreground elements are moved sideways in opposite directions from each other.
The longer a viewer looks at stereoscopic images, the stronger the images begin to appear. Moving further away from the 3D images can also improve the anaglyphic 3D effect, and seeing the image from different angles can produce interesting optical illusions. For instance, it can seem as if the eyes of a figure are following the viewer around.
The use of anaglyph 3D is becoming increasingly popular in the art, film and science fields. 3D movies use the anaglyphic principle and there have also been many 3D TV programs. Artists have used anaglyph 3D to give a 3D depth to paintings and illustrations. Anaglyph images are used on websites, with Blu-ray® HD discs and on video displays.
In science, anaglyph 3D is a boon for space, geological, chemical and biological imagery that needs to be presented with a degree of depth. 3D ultrasound is used to create stereoscopic images of the heart and other internal organs in medicine, and 3D images are used in science books to be viewed with 3D glasses. Researchers and students alike find it easier to understand scientific concept when these are presented in 3D.
It is possible that some people may have a problem with the 3D glasses that are needed to view anaglyph 3D images. Donning these glasses for extended periods may produce a disorienting effect on viewers. Sometimes it may lead to eyestrain and headaches. It will help to exercise moderation in use.