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{{Short description|Method of representing images in 3D}}
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[[Image:Stereograph as an educator - anaglyph.jpg|thumb|200px|Stereo image anaglyphed for red (left eye) and cyan (right eye) filters.]]
{{Use American English|date=March 2019}}
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[[File:Hammer anaglyph (14656149338).jpg|thumb|A simple red-cyan anaglyph image {{3D glasses}}]]
[[File:3D dusk on Desert.jpg|thumb|Anaglyph of Saguaro National Park at dusk {{3D glasses}}]]
[[File:Persepolis (By Abdolazim Hasseli).jpg|thumb|Anaglyph of a column head in [[Persepolis]], Iran {{3D glasses}}]]
[[File:BinocularRivalry.svg|thumb|200px|An image demonstrating [[binocular rivalry]]. If you view the image with red-cyan 3D glasses, the text will alternate between '''Red''' and '''Blue'''.{{3D glasses}}]]
'''Anaglyph 3D''' is the [[Stereoscopy|stereoscopic]] 3D effect achieved by means of encoding each eye's image using filters of different (usually [[Complementary colors|chromatically opposite]]) colors, typically [[red]] and [[cyan]]. Anaglyph 3D images contain two differently filtered colored images, one for each eye. When viewed through the "color-coded" "anaglyph glasses", each of the two images is visible to the eye it is intended for, revealing an integrated stereoscopic image. The [[visual cortex]] of the brain fuses this into the perception of a three-dimensional scene or composition.
 
Anaglyph images have seen a recent resurgence due to the presentation of images and video on the [[World Wide Web|Web]], [[Blu-ray Disc]]s, 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. The norm is red and cyan, with red being used for the left channel. The cheaper filter material used in the monochromatic past dictated red and blue for convenience and cost. There is a material improvement of full color images with the cyan filter, especially for accurate skin tones.
[[Image:Stereograph as an educator.jpg|thumb|200px|Stereogram source image for the anaglyph above.]]
 
Video games, theatrical films, and DVDs can be shown in 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 investigation, called [[STEREO]], which uses two orbital vehicles to obtain the 3D images of the sun. Other applications include geological illustrations by the [[United States Geological Survey]], and various online museum objects. A recent application is for stereo imaging of the heart using 3D ultra-sound with plastic red/cyan glasses.
'''Anaglyph (stereoscopic) images''' in either [[black and white]] or color are viewed, using "mutually cancelling" color filters mounted in paper or plastic glasses.
 
Anaglyph images are much easier to view than either parallel (diverging) or crossed-view pairs [[stereoscopy|stereograms]]. However, these side-by-side types offer bright and accurate color rendering, not easily achieved with anaglyphs. Also, extended use of the "color-coded" "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. Recently,{{reltime|date=September 2023}} cross-view prismatic glasses with adjustable masking have appeared, that offer a wider image on the new HD video and computer monitors.
In the past this was a purely photographic process, but now computer image processing techniques are used to composite the images. Two discrete views are combined in two layers in the digital image. These views
incorporate parallax of the slightly different viewpoints into an integrated [[stereoscopic imaging | stereoscopic image]]. The composited stereo image must then be viewed with "anaglyph glasses", which use color filters to create a discrete luminance separation of the views, providing a slightly different perspective to each eye. The [[visual cortex]] of the brain fuses this into perception of a three dimensional scene or composition.
 
== History ==
Anaglyph images have seen a recent resurgence due to the presentation of images and video on the internet, CDs, and even in print. Low cost paper frames that hold accurate color filters, or various plastic framed glasses that can provide longtime durability, and less diffraction of light. 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 2006 ongoing solar investigation, called [[STEREO]], which uses two orbital vehicles to obtain the 3D images of the sun. Other applications include geological illustrations by the [[USGS]], and various online museum objects.
The oldest known description of anaglyph images was written in August 1853 by W. Rollmann in [[Stargard]] about his "Farbenstereoscope" (color stereoscope). He had the best results viewing a yellow/blue drawing with red/blue glasses. Rollmann found that with a red/blue drawing the red lines were not as distinct as yellow lines through the blue glass.<ref>{{Citation |last=Rollmann |first=W. |year=1853 |title=Zwei neue stereoskopische Methoden |journal=Annalen der Physik |language=de |volume=90 |issue=9 |pages=186–187 |doi=10.1002/andp.18531660914 |ref=Rollmann |url=https://books.google.com/books?id=cmYEAAAAYAAJ&q=rollmann%20stereoskopische&pg=PA186 |bibcode=1853AnP...166..186R}}</ref>
 
In 1858, in France, {{Interlanguage link|Joseph D'Almeida|fr|Joseph-Charles d'Almeida|vertical-align=sup}} delivered a report to l'Académie des sciences describing how to project three-dimensional [[magic lantern]] slide shows using red and green filters to an audience wearing red and green goggles.<ref>{{cite news |last1=D'Almeida |first1=Joseph Charles |title=Nouvel appareil stéréoscopique |language=fr |trans-title=A New Stereoscopic Device |page=61 |url=https://gallica.bnf.fr/ark:/12148/bpt6k3004t/f61.image |format=image |type=Lecture |website=Gallica |year=1858}}</ref> Subsequently, he was chronicled as being responsible for the first realisation of 3D images using anaglyphs.<ref>{{cite news |last1=Picard |first1=Emile |title=La Vie et L'œuvre de Gabriel Lippmann (membre de la section de physique générale) |language=fr |trans-title=The Life and Work of Gabriel Lippmann |page=3 |url=http://www.academie-sciences.fr/pdf/dossiers/Picard/Picard_pdf/Picard_Lippmann.pdf |type=Public Lecture |website=academie-sciences.fr |publisher=Institut de France. Académie des Sciences |date=December 14, 1931}}</ref>
Video games, theatrical films, and DVDs can be shown in the anaglyph 3D process. Anaglyph images are much easier to view than either parallel sighting or crossed eye stereograms. However, these side-by-side types offer bright and accurate color rendering, not easily achieved with anaglyphs. With the techniques outlined below it is possible to convert stereo pairs from any source into anaglyph images.
 
[[Louis Ducos du Hauron]] produced the first printed anaglyphs in 1891.<ref>{{Cite web |title=Louis Ducos du Hauron {{!}} French physicist and inventor {{!}} Britannica |url=https://www.britannica.com/biography/Louis-Ducos-du-Hauron |access-date=2022-05-26 |website=www.britannica.com |language=en}}</ref> This process consisted of printing the two negatives which form a stereoscopic photograph on to the same paper, one in blue (or green), one in red. The viewer would then use colored glasses with red (for the left eye) and blue or green (right eye). The left eye would see the blue image which would appear black, whilst it would not see the red; similarly the right eye would see the red image, this registering as black. Thus a three dimensional image would result.
==Producing anaglyph images==
In historical methods using camera filters, two images from the perspective of the left and right eyes are projected or printed together as a single image, one side through a [[red]] filter and the other side through a contrasting color such as [[blue]] or [[green]] or [[cyan]]. As outlined below, one may also use an [[Digital image processing|image processing computer program]] to simulate the effect of using color filters, using as a source image a pair of either color or monochrome images. Since the turn of the century, most filtering, both in glasses and processing have favored primary red, for the left eye, and cyan (which is equal parts blue and green) for the right eye. These 3 colors cover the entire visible spectrum, providing more natural color.
Popular professional programs such as [[Adobe Photoshop]] provide the basic digital tools for processing of anaglyphs. Simple, low cost programs dedicated to anaglyph creation are also available. In practice, the left eye image is filtered to remove
blue & green. The right eye image is filtered to remove red. The two images are usually positioned in the compositing phase in
close overlay registration. In [[Photoshop]]. for example a function called "screen" allows the two filtered layers to be combined transparently, on eachother.
 
William Friese-Green created the first three-dimensional anaglyphic motion pictures in 1889, which had public exhibition in 1893.<ref>{{Cite web |title=Silent Era : Progressive Silent Film List |url=https://www.silentera.com/PSFL/data/F/FrieseGreeneStereoscop1893.html |access-date=2022-05-19 |website=www.silentera.com}}</ref> 3-D films enjoyed something of a boom in the 1920s. <ref>{{Cite web |last=Patterson |first=John |date=2009-08-19 |title=John Patterson: A history of 3D cinema |url=http://www.theguardian.com/film/2009/aug/20/3d-film-history |access-date=2022-05-26 |website=the Guardian |language=en}}</ref> As late as 1954, films such as ''[[Creature from the Black Lagoon]]'' remained very successful. Originally shot and exhibited using the Polaroid system, ''Creature from the Black Lagoon'' was successfully reissued much later in an anaglyph format so it could be shown in cinemas without the need for special equipment. Although not anaglyphic, ''[[Jaws 3|Jaws 3-D]]'' was a box-office success in 1983. At present the excellent quality of computer displays and user-friendly stereo-editing programs offer new and exciting possibilities for experimenting with anaglyph stereo.
==How Anaglyph works==
Viewing anaglyphs through appropriately coloured glasses results in each eye seeing a slightly different picture. In a red-blue anaglyph, for instance, the eye covered by the red filter sees the red parts of the image as "white", and the blue parts as "black" (with the brain providing some adaption for colour); the eye covered by the blue filter perceives the opposite effect. True white or true black areas are perceived the same by each eye. The brain blends together the image it receives from each eye, and interprets the differences as being the result of different distances. This creates a normal stereograph image without requiring the viewer to cross his or her eyes.
 
The American photographic artist [[Claudia Kunin]] began using this rendering technique to produce fine art prints in 2010.<ref>{{cite web|title=Digital Darkroom: An Exploration of Altered Realities|publisher=[[ABC News (United States)|ABC News]]|author=Lawrence Lai|date=25 November 2011|url=https://abcnews.go.com/blogs/headlines/2011/11/digital-darkroom-an-exploration-of-altered-realities-2}}</ref>
==3D in the movies==
From 1952 to 1954, 3D movies became very popular with more than 30 titles enjoying wide distribution , then faded away as the competing [[Cinemascope]] widescreen systems became an attraction for theaters. Contrary to frequently stated claims{{fact}}, 98% of the screenings in theaters in the fifties were presented in [[Polarized glasses|polarized]], dual projector interlocked format… not anaglyph with colored glasses according to American 3d historians, Ray Zone and Dan Symnes in their several books on 3d.
 
The term "3-D" was coined in the 1950s.{{cn|date=June 2021}} In 1953, the anaglyph had begun appearing sporadically in newspapers, magazines and comic books.
==Modern 3D movies==
''[[Spy Kids|Spy Kids 3D]]'' was commercially successful in theaters using anaglyph paper glasses in 2003. The DVD did not sell or rent well, due to video retailers not wanting to deal with the paper glasses. Polar Express, in 2004, used the superior IMAX polarized method for 3D. That film made $62 million dollars in less than 90 theaters over two holiday seasons. It earned 14 times as much as the 2D version of the film,per screen, which is "un-precedented"{{fact}}. A second, anaglyph film, 2005 by Robert Rodriquez, ''[[The Adventures of Shark Boy & Lava Girl]]'' failed to recover investment by many millions. The film had been processed in a highly "desaturated" 3D style, which was not very appealing. Disney released their 2005 ''[[Chicken Little]]'' in about 84 theaters, in digital polarized 3D. It earned nearly 3 times the gross of the much wider 2D release. 6 new films were slated for 3D release in 2006. They include ''[[Monster House (film)|Monster House]]'', portions of the IMAX version of ''[[Superman Returns]]'', ''[[The Ant Bully]]'', ''[[Open Season]]'', ''[[Nightmare before Christmas]]'' (converted to 3D), ''[[Fly Me to the Moon]]'', all in [[Polarized glasses|polarized 3D]]. Anaglyph may have more applicability in the home market, should this crop of polarized 3D films prove commercially viable in theaters. At this point, anaglyph offers the only practical method for wide distribution of 3D home DVDs, or HD broadcasting in 3D, without costly electronic glasses.
 
== Production ==
==Conversion from 2D flat to 3D anaglyph==
{{multiple image |direction=vertical |align=vertical
In recent years computer technology and professional skills have made it practical to convert still images, movies & video to 3D. Color anaglyph looks particularly good in HD, with animation content. See NASA Illustration converted to Anachrome 3D.
|image1=Stereograph as an educator - anaglyph.jpg |caption1=Stereo monochrome image anaglyphed for red (left eye) and cyan (right eye) filters {{3D glasses}}
A feature film like ''[[Star Wars]]'' might cost as much as $10 million to convert for theater showing. The HD DVD 3D version might cost a fifth of that amount.
|image2=Stereograph as an educator.jpg |caption2=Stereogram source image for the anaglyph above
}}
 
=== Anaglyph from stereo pairs ===
Note: Information below relates to "traditional methodology", not the newer techniques, mentioned above.
A stereo pair is a pair of images from slightly different perspectives at the same time. Objects closer to the camera(s) have greater differences in appearance and position within the image frames than objects further from the camera.
 
Historically cameras captured two color filtered images from the perspective of the left and right eyes which were projected or printed together as a single image, one side through a [[red]] filter and the other side through a contrasting color such as [[blue]] or [[green]] or mixed [[cyan]]. One may typically use an [[Digital image processing|image processing computer program]] to simulate the effect of using color filters, using as a source image a pair of either color or monochrome images. This is called channel mixing, a kind of [[digital compositing]] or [[blend modes|blending]].
==Viewing==
[[Image:3d_glasses.jpg|thumb|right|red and cyan glasses for viewing anaglyphs.]]
 
In the 1970s filmmaker Stephen Gibson filmed direct anaglyph [[blaxploitation]] and [[adult movies]]. His "Deep Vision" system replaced the original camera lens with two color-filtered lenses focused on the same film frame.<ref>{{cite book |url=https://books.google.com/books?id=L_aWx3hHiD0C&pg=PA37 |title=3-D Filmmakers: Conversations with Creators of Stereoscopic Motion Pictures |first=Ray |last=Zone |date=May 7, 2018 |publisher=Scarecrow Press |isbn=9780810854376 |access-date=May 7, 2018 |via=Google Books}}</ref> In the 1980s, Gibson patented his mechanism.<ref>{{cite web |url=https://patents.google.com/patent/US4295153 |title=US Pat. 4295153, retrieved Jan 17, 2011 |website=google.com |access-date=May 7, 2018}}</ref>
A pair of eyeglasses with two filters of the same colors used on the camera (or simulated by image processing software manipulations) is worn by the viewer. In the case above the red lens over the left eye allows only the cyan part of the anaglyph image through to that eye, while the cyan (blue/green) lens over the right eye allows only the red part of the image through to that eye. Portions of the image that are red will appear dark through the cyan filter, while cyan portions will appear dark through the red filter. Each eye therefore sees only the perspective it is supposed to see.
 
Many computer graphics programs provide the basic tools (typically layering and adjustments to individual color channels to filter colors) required to prepare anaglyphs from stereo pairs. In simple practice, the left eye image is filtered to remove blue and green, which is achieved by multiplying each of the pixels in the left image by solid red (#FF0000). The right eye image is filtered to remove red, by multiplying its pixels by solid cyan (#00FFFF). The two images are usually positioned in the compositing phase in close overlay registration (of the main subject), and are then combined using an [[blend modes#Addition|additive blend mode]]. Plugins for some of these programs as well as programs dedicated to anaglyph preparation are available which automate the process and require the user to choose only a few basic settings.
===Compensating anaglyph glasses===
Simple sheet or uncorrected molded glasses do not compensate for the 250 nanometer difference in the wave lengths of the red-cyan filters. With simple glasses, the red filter image can be blurry when viewing a close computer screen or printed image since the retinal focus differs from the image through the cyan filter, which dominates the eyes' focusing. Better quality molded plastic glasses employ a compensating differential diopter power to equalize the red filter focus shift relative to the cyan.
 
=== Stereo conversion (single 2D image to 3D) ===
The downside, however, to diopter correction on one lens is that, as anybody with corrective glasses having two different diopters knows, one image is a slightly different size than the other. The problem is especially noticeable when looking above or below the centers of the lenses, where vertical discrepancies may be uncomfortable.
There also exist methods for making anaglyphs using only one image, a process called [[stereo conversion]]. In one, individual elements of a picture are horizontally offset in one layer by differing amounts with elements offset further having greater apparent changes in depth (either forward or back depending on whether the offset is to the left or right). This produces images that tend to look like elements are flat standees arranged at various distances from the viewer similar to cartoon images in a [[View-Master]].
 
A more sophisticated method involves use of a [[depth map]] (a false color image where color indicates distance, for example, a grayscale depth map could have lighter indicate an object closer to the viewer and darker indicate an object further away).<ref>[http://myweb.cableone.net/amh2004/2D_3D.html The two best methods for creating anaglyphs from only one image.] {{webarchive |url=https://web.archive.org/web/20110728080738/http://myweb.cableone.net/amh2004/2D_3D.html |date=July 28, 2011 }}</ref> As for preparing anaglyphs from stereo pairs, stand-alone software and plug-ins for some graphics apps exist which automate production of anaglyphs (and stereograms) from a single image or from an image and its corresponding depth map.
==Making an anaglyph image==
===Anaglyphs from monochrome images===
[[Image:TgMures stereo image.jpg|thumb|150px|right|Anaglyph from monochrome images.]]
 
As well as fully automatic methods of calculating depth maps (which may be more or less successful), depth maps can be drawn entirely by hand. Also developed are methods of producing depth maps from sparse or less accurate depth maps.<ref>{{Cite web |url=http://people.eecs.berkeley.edu/~barron/BarronPoole2015.pdf |title=The Fast Bilateral Solver |last=Barron & Poole |access-date=July 3, 2016}}{{Dead link|date=March 2017}}</ref> A sparse depth map is a depth map consisting of only a relatively few lines or areas which guides the production of the full depth map. Use of a sparse depth map can help overcome auto-generation limitations. For example, if a depth finding algorithm takes cues from image brightness an area of shadow in the foreground may be incorrectly assigned as background. This misassignment is overcome by assigning the shaded area a close value in the sparse depth map.
The following method assumes that the stereo pair is available as a digitized image and that access to general purpose image processing software and computer is available.
 
== Mechanics ==
Starting with a pair of color images, or a sepia (toned) image, first convert each to grayscale (shades varying between black and white). Select the right image and paste it into a new document. Convert the new document to color (it still looks black and white, with all channels identical). Returning to the grayscale stereo pair select only the red channel of the left image and copy that channel to the clipboard. Select new the anaglyph document as the destination window. Using the ''channels'' window select the red channel and paste in the left image. The images may then be flattened, color adjustments applied as outlined below, and the image saved in an approprate transmission and viewing format such as [[JPEG]].
Viewing anaglyphs through spectrally opposed glasses or gel filters enables each eye to see independent left and right images from within a single anaglyphic image. Red-cyan filters can be employed because our vision processing systems use red and cyan comparisons, as well as blue and yellow, to determine the color and contours of objects.<ref>[http://www.lincolntom.com/documents/About%203D.doc Exercises in Three Dimensions: About 3D] {{webarchive |url=https://web.archive.org/web/20150222204340/http://www.lincolntom.com/documents/About%203D.doc |date=February 22, 2015 }}, Tom Lincoln, 2011</ref>
 
In a red-cyan anaglyph, the eye viewing through the red filter sees red within the anaglyph as "white", and the cyan within the anaglyph as "black". The eye viewing through the cyan filter perceives the opposite.<ref>[http://www.lincolntom.com/documents/About%203D.doc Exercises in Three Dimensions: About 3D] {{webarchive |url=https://web.archive.org/web/20150222204340/http://www.lincolntom.com/documents/About%203D.doc |date=February 22, 2015 }}</ref>
===Anaglyphs containing color information===
Using color images, replace the red channel of the right-eye image with the red channel of the left-eye image. Here's how: select the entire right eye image (if the original is a crossed eye stereogram this will be on the left) and make a new document. Paste the right eye image in. Move the selection to the left eye image (with consideration as above for crossed eye stereograms) and using the channels dialog select the red channel. Copy the red channel from this source image. Select the new document and select the red channel. Paste the left eye image into the red channel. Depending upon the colors this might [[Image:LGColorAnaglyphSceneMR.jpg|thumb|right|300px|Color anaglyph taken using two cameras about 40cm (16in) apart for enhanced depth effect.]]look rather good as a color image (but not exactly true to the original color). Eye sensitivity balance can be improved by selecting the green channel and reducing it using a linear curve selection (e.g. reduce to 12.5%). Select the blue channel and reduce somewhat less (e.g. reduce by 5%). This action compensates for the eye's lower sensitivity to red and its high sensitivity to green, but may induce bleed through (you may see ghost images on one side or to each side of an object). Without the anaglyph glasses the picture will appear reddish and somewhat dimmer, but the overall effect is improved when the glasses are used. The dimness can be corrected by increasing the overall brightness 15 to 20% and the contrast 10 to 15%. All of these adjustments will depend upon color balance, brightness, and contrast of the original image and the nature of the subject material.
 
Actual black or white in the anaglyph display, being void of color, are perceived the same by each eye. The brain blends together the red and cyan channeled images as in regular viewing but only green and blue are perceived. Red is not perceived because red equates with white through red gel and is black through cyan gel. Green and blue, however, are perceived through cyan gel.{{fact|date=September 2022}}
Using color information, it is possible to obtain reasonable (but not accurate) blue sky, green vegetation, and appropriate skin tones. Color information appears disruptive when used for brightly colored and high contrast objects such as signage, toys, and patterned clothing when these contain colors that are close to red or cyan.
 
===Depth adjustment=Types ==
(The adjustment suggested in this is section is applicable to any type of stereogram but is particularly appropriate when anaglyphed images are to be viewed on a computer screen or on printed matter.)
 
=== Complementary color ===
[[Image:TwinPeaks glyph th.gif|thumb|none|527px|Image as originally presented by [[NASA]] with foreground spilling from the frame. This is a two-color (red-cyan) anaglyph from the [[Mars Pathfinder]] mission. To view, use a red filter for the left eye and a cyan filter for the right eye. Note that the distant mountain images are aligned, placing them at the screen, and the confusing appearance in the lower right corner.]]
[[File:Anaglyph glasses.png|thumb|Paper anaglyph filters produce an acceptable image at low cost and are suitable for inclusion in magazines.]]
[[File:Anaglyph - formerly attributed to Piero della Francesca.png|thumb|Piero della Francesca, Ideal City in an Anaglyph version {{3D glasses}}]]
 
Complementary color anaglyphs employ one of a pair of complementary color filters for each eye. The most common color filters used are red and cyan. Employing [[tristimulus]] theory, the eye is sensitive to three primary colors, red, green, and blue. The red filter admits only red, while the cyan filter blocks red, passing blue and green (the combination of blue and green is perceived as cyan). If a paper viewer containing red and cyan filters is folded so that light passes through both, the image will appear black. Another recently{{reltime|date=September 2023}} introduced form employs blue and yellow filters. (Yellow is the color perceived when both red and green light passes through the filter.)
[[Image:TwinPeaksDepthAdjusted.jpg|thumb|none|520px|Image adjusted so that most objects appear to be beyond the frame. Note that the mountain images are now separated when viewed without the glasses. This follows the rule for a red left eye filter when distant objects are beyond the image plane: RRR-Red to Right Receding in the image as it appears without wearing the filters.]]
 
Anaglyph images have seen a recent resurgence because of the presentation of images on the Internet. Where traditionally, this has been a largely black & white format, recent digital camera and processing advances have brought very acceptable color images to the internet and DVD field. With the online availability of low cost paper glasses with improved red-cyan filters, and plastic framed glasses of increasing quality, the field of 3D imaging is growing quickly. Scientific images where depth perception is useful include, for instance, the presentation of complex multi-dimensional data sets and stereographic images of the surface of [[Mars]]. With the recent release of 3D DVDs, they are more commonly being used for entertainment. Anaglyph images are much easier to view than either parallel sighting or crossed eye stereograms, although these types do offer more bright and accurate color rendering, most particularly in the red component, which is commonly muted or desaturated with even the best color anaglyphs. A compensating technique, commonly known as Anachrome, uses a slightly more transparent cyan filter in the patented glasses associated with the technique. Processing reconfigures the typical anaglyph image to have less parallax to obtain a more useful image when viewed without filters.
 
=== Compensating focus diopter glasses for red-cyan method ===
Simple sheet or uncorrected molded glasses do not compensate for the 250 nanometer difference in the wavelengths of the red-cyan filters. With simple glasses the red filter image can be blurry when viewing a close computer screen or printed image since the retinal focus differs from the cyan filtered image, which dominates the eyes' focusing. Better quality molded plastic glasses employ a compensating differential diopter power to equalize the red filter focus shift relative to the cyan. The direct view focus on computer monitors has been recently{{reltime|date=September 2023}} improved by manufacturers providing secondary paired lenses, fitted and attached inside the red-cyan primary filters of some high-end anaglyph glasses. They are used where very high resolution is required, including science, stereo macros, and animation studio applications. They use carefully balanced cyan (blue-green) acrylic lenses, which pass a minute percentage of red to improve skin tone perception. Simple red/blue glasses work well with black and white, but the blue filter is unsuitable for human skin in color. U.S. Patent No. 6,561,646 was issued to the inventor in 2003. In the trade,
the label "www.anachrome" is used to label diopter corrected 3D glasses covered by this patent.
 
=== (ACB) 3-D ===
(ACB) 'Anaglyphic Contrast Balance' is a patented anaglyphic production method by Studio 555.<ref name="NZ Patent 505513, AUS Patent 785021, UK Patent GB 2366114, Canada 2352272">{{cite web |url=http://www.acb3d.com/whatisacb3d.html |title=(ACB) 3-D 'Anaglyphic Contrast Balance' Anaglyphic 3-D production method. |url-status = live|archive-url=https://web.archive.org/web/20120510192200/http://www.acb3d.com/whatisacb3d.html |archive-date=May 10, 2012 }}</ref> Retinal Rivalry of color contrasts within the color channels of anaglyph images is addressed.
 
Contrasts and details from the stereo pair are maintained and re-presented for view within the anaglyph image. The (ACB) method of balancing the color contrasts within the stereo pair enables a stable view of contrast details, thus eliminating retinal rivalry. The process is available for red/cyan color channels but may use any of the opposing color channel combinations. As with all stereoscopic anaglyphic systems, screen or print, the display color should be RGB accurate and the viewing gels should match the color channels to prevent double imaging. The basic (ACB) method adjusts red, green and blue, but adjusting all six color primaries is preferred.
 
The effectiveness of the (ACB) process is proven with the inclusion of primary color charts within a stereo pair. A contrast-balanced view of the stereo pair and color charts is evident in the resulting (ACB) processed anaglyph image. The (ACB) process also enables black and white (monochromatic) anaglyphs with contrast balance.
 
Where full color to each eye is enabled via alternating color channels and color-alternating viewing filters, (ACB) prevents shimmer from pure-colored objects within the modulating image. Vertical and diagonal parallax is enabled with concurrent use of a horizontally oriented lenticular or parallax barrier screen. This enables a Quadrascopic full color holographic effect from a monitor.
 
=== ColorCode 3-D ===
[[ColorCode 3-D]] was deployed in the 2000s and uses amber and blue filters. It is intended to provide the perception of nearly full color viewing (particularly within the [[RG color space]]) with existing television and paint mediums. One eye (left, amber filter) receives the cross-spectrum color information and one eye (right, blue filter) sees a monochrome image designed to give the depth effect. The human brain ties both images together.
 
Images viewed without filters will tend to exhibit light-blue and yellow horizontal fringing. The backwards compatible 2D viewing experience for viewers not wearing glasses is improved, generally being better than previous red and green anaglyph imaging systems, and further improved by the use of digital post-processing to minimize fringing. The displayed hues and intensity can be subtly adjusted to further improve the perceived 2D image, with problems only generally found in the case of extreme blue.
 
The blue filter is centered around 450&nbsp;nm and the amber filter lets in light at wavelengths at above 500&nbsp;nm. Wide spectrum color is possible because the amber filter lets through light across most wavelengths in spectrum and even has a small leakage of the blue color spectrum. When presented the original left and right images are run through the ColorCode 3-D encoding process to generate one single ColorCode 3-D encoded image.
 
In the United Kingdom, television station [[Channel 4]] commenced broadcasting a series of programs encoded using the system during the week of November 16, 2009.<ref>{{cite web |url=http://www.channel4.com/programmes/3d-week/articles/3d-week |archive-url=https://web.archive.org/web/20091112101613/http://www.channel4.com/programmes/3d-week/articles/3d-week |url-status = dead|archive-date=November 12, 2009 |title=Announcements |work=3D Week |access-date=November 18, 2009 |date=October 11, 2009 |quote=glasses that will work for Channel 4’s 3D week are the Amber and Blue ColourCode 3D glasses}}</ref> Previously the system had been used in the United States for an "all 3-D advertisement" during the [[Super Bowl XLIII|2009 Super Bowl]] for [[SoBe]], [[Monsters vs. Aliens]] animated movie and an advertisement for the [[Chuck (TV series)|Chuck]] television series in which the full episode the following night used the format.
 
=== Inficolor 3D ===
Developed by [[TriOviz]], Inficolor 3D is a patent pending stereoscopic system, first demonstrated at the [[International Broadcasting Convention]] in 2007 and deployed in 2010. It works with traditional 2D flat panels and HDTV sets and uses expensive glasses with complex color filters and dedicated [[image processing]] that allow natural [[color perception]] with a 3D experience. This is achieved through having the left image using the green channel only and the right using the red and blue channels with some added post processing, which the brain then combines the two images to produce a nearly full color experience. When observed without glasses, some slight doubling can be noticed in the background of the action which allows watching the movie or the video game in 2D without the glasses. This is not possible with traditional brute force anaglyphic systems.<ref>[http://www.digitalcinemareport.com/Darkworks-Trioviz-3D Digitalcinemareport.com The Games We Play] by Michael Karagosian {{webarchive|url=https://web.archive.org/web/20120319030821/http://www.digitalcinemareport.com/Darkworks-Trioviz-3D |date=March 19, 2012 }}</ref>
 
Inficolor 3D is a part of TriOviz for Games Technology, developed in partnership with TriOviz Labs and Darkworks Studio. It works with [[PlayStation 3|Sony PlayStation 3]] (Official PlayStation 3 Tools & Middleware Licensee Program)<ref>[http://www.prnewswire.com/news-releases/triovizr-for-games-adds-3d-tv-support-for-console-titles-99041174.html PRnewswire.com] {{webarchive|url=https://web.archive.org/web/20120115033142/http://www.prnewswire.com/news-releases/triovizr-for-games-adds-3d-tv-support-for-console-titles-99041174.html |date=January 15, 2012 }}, TriOviz for Games Adds 3D TV Support for Console Titles</ref> and [[Xbox 360|Microsoft Xbox 360]] consoles as well as PC.<ref name="joystiq.com">[http://www.joystiq.com/2010/10/11/mark-rein-trioviz-interview/ Joystiq.com] {{webarchive|url=https://web.archive.org/web/20120312142947/http://www.joystiq.com/2010/10/11/mark-rein-trioviz-interview/ |date=March 12, 2012 }}, Epic's Mark Rein goes in-depth with Unreal Engine 3's TriOviz 3D</ref><ref name="epicgames.com">[http://www.epicgames.com/news/darkworks-trioviz-for-games-sdk-brings-3d-capabilities-to-unreal-engine-3 Epicgames.com] {{webarchive|url=https://web.archive.org/web/20120309110608/http://epicgames.com/news/darkworks-trioviz-for-games-sdk-brings-3d-capabilities-to-unreal-engine-3 |date=March 9, 2012 }}, TriOviz for Games Technology Brings 3D Capabilities to Unreal Engine 3</ref> TriOviz for Games Technology was showcased at [[Electronic Entertainment Expo]] 2010 by [[Mark Rein (software executive)|Mark Rein]] (vice-president of [[Epic Games]]) as a 3D tech demo running on an Xbox 360 with [[Gears of War 2]].<ref>{{cite web |author=computerandvideogames.com Tim Ingham |url=http://www.computerandvideogames.com/252372/news/epic-makes-3d-gears-of-war-2/?attr=cvg-general-rss&skip=yes |archive-url=https://archive.today/20120728140333/http://www.computerandvideogames.com/252372/news/epic-makes-3d-gears-of-war-2/?attr=cvg-general-rss&skip=yes |url-status = dead|archive-date=July 28, 2012 |title=E3 2010: Epic makes 3D Gears Of War 2 - We've seen it. It's mega. But retail release not planned |publisher=Computer and Video Games.com |date=June 17, 2010 |access-date=March 4, 2012}}</ref> In October 2010 this technology has been officially integrated in [[Unreal Engine 3]],<ref name="joystiq.com"/><ref name="epicgames.com"/> the computer game engine developed by Epic Games.
 
[[File:Stereoscopic-three-dimensional-visualization-applied-to-multimodal-brain-images-clinical-Video1.ogv|thumb|Stereo 3D visualization video of the surface of a [[human brain]] {{3D glasses}}]]
Video games equipped with TriOviz for Games Technology are: ''[[Batman: Arkham Asylum|Batman Arkham Asylum: Game of the Year Edition]]'' for [[PS3]] and [[Xbox 360]] (March 2010),<ref>[https://www.engadget.com/2010/03/12/darkworks-shows-off-trioviz-for-games-2d-to-3d-sdk-we-get-a-goo?icid=sphere_blogsmith_inpage_engadget Engadget.com] {{webarchive|url=https://web.archive.org/web/20121022111359/http://www.engadget.com/2010/03/12/darkworks-shows-off-trioviz-for-games-2d-to-3d-sdk-we-get-a-goo?icid=sphere_blogsmith_inpage_engadget |date=October 22, 2012 }} Darkworks shows off TriOviz for Games 2D-to-3D SDK, we get a good look</ref><ref>[http://spong.com/feature/10110086/Review-Batman-Arkham-Asylum-Game-of-the-Year-Edition Spong.com] {{webarchive|url=https://web.archive.org/web/20100328083502/http://spong.com/feature/10110086/Review-Batman-Arkham-Asylum-Game-of-the-Year-Edition |date=March 28, 2010 }}, Reviews of Batman Arkham Asylum Game of the Year Edition in 3D</ref><ref>[http://www.batmanarkhamasylum.com/blogs/9 Batmanarkhamasylum.com] {{webarchive|url=https://web.archive.org/web/20110707214613/http://www.batmanarkhamasylum.com/blogs/9 |date=July 7, 2011 }}, How do you add another dimension to one of the best games of 2009?</ref> ''[[Enslaved: Odyssey to the West#Pigsy's Perfect 10|Enslaved: Odyssey to the West + DLC Pigsy's Perfect 10]]'' for [[PS3]] and [[Xbox 360]] (Nov. 2010),<ref>[http://enslaved.namco.com/extras/pigsydlc/ Enslaved.namco.com] Pigsy's DLC in 3D {{webarchive|url=https://web.archive.org/web/20101112034402/http://enslaved.namco.com/extras/pigsydlc |date=November 12, 2010 }}</ref><ref>[http://www.gamesradar.com/f/enslaved-pigsys-perfect-10-dlc-review/a-2010121718646656088 Gamesradar.com] {{webarchive|url=https://web.archive.org/web/20101226043238/http://www.gamesradar.com/f/enslaved-pigsys-perfect-10-dlc-review/a-2010121718646656088 |date=December 26, 2010 }} Enslaved: Pigsy's DLC review</ref> ''[[Thor: God of Thunder]]'' for [[PS3]] and [[Xbox 360]] (May 2011), ''[[Green Lantern: Rise of the Manhunters]]'' for [[PS3]] and [[Xbox 360]] (June 2011), ''[[Captain America: Super Soldier]]'' for [[PS3]] and [[Xbox 360]] (July 2011). ''[[Gears of War 3]]'' for [[Xbox 360]] (September 2011), ''[[Batman: Arkham City]]'' for [[PS3]] and [[Xbox 360]] (October 2011), ''[[Assassin's Creed: Revelations]]'' for [[PS3]] and [[Xbox 360]] (November 2011), and ''[[Assassin's Creed III]]'' for [[Wii U]] (November 2012). The first DVD/Blu-ray including Inficolor 3D Tech is: ''[[Battle for Terra|Battle for Terra 3D]]'' (published in [[France]] by [[Pathé]] & Studio 37 - 2010).
 
=== Anachrome red/cyan filters ===
{{unreferenced section|date=February 2013}}
[[File:Plastic 3D glasses.jpg|thumb|Anachrome glasses]]
[[File:1930 Cord.jpg|thumb|Full color Anachrome red (left eye) and cyan (right eye) filters {{3D glasses|color=anachrome}}]]
A variation on the anaglyph technique from the early 2000s is called "Anachrome method". This approach is an attempt to provide images that look nearly normal, without glasses, for small images, either 2D or 3D, with most of the negative qualities being masked innately by the small display. Being "compatible" for small size posting in conventional websites or magazines. Usually a larger file can be selected that will fully present the 3D with the dramatic definition. The 3D (Z axis) depth effect is generally more subtle than simple anaglyph images, which are usually made from wider spaced stereo pairs. Anachrome images are shot with a typically narrower stereo base, (the distance between the camera lenses). Pains are taken to adjust for a better overlay fit of the two images, which are layered one on top of another. Only a few pixels of non-registration give the depth cues. The range of color perceived, is noticeably wider in Anachrome image, when viewed with the intended filters. This is due to the deliberate passage of a small (1 to 2%) of the red information through the cyan filter. Warmer tones can be boosted, because each eye sees some color reference to red. The brain responds in the mental blending process and usual perception. It is claimed to provide warmer and more complex perceived skin tones and vividness.
 
=== Interference filter systems ===
[[File:Dolby 3D.png|thumb|upright|left|Interference principle]]
This technique uses specific wavelengths of red, green, and blue for the right eye, and different wavelengths of red, green, and blue for the left eye. Eyeglasses which filter out the very specific wavelengths allow the wearer to see a full color 3D image. Special interference filters (dichromatic filters) in the glasses and in the projector form the main item of technology and have given the system this name. It is also known as spectral comb filtering or wavelength multiplex visualization. Sometimes this technique is described as a "super-anaglyph" because it is an advanced form of spectral-multiplexing which is at the heart of the conventional anaglyph technique. This technology eliminates the expensive silver screens required for polarized systems such as [[RealD]], which is the most common 3D display system in theaters. It does, however, require much more expensive glasses than the polarized systems.
 
[[Dolby 3D]] uses this principle. The filters divide the visible color spectrum into six narrow bands – two in the red region, two in the green region, and two in the blue region (called R1, R2, G1, G2, B1 and B2 for purposes of this description). The R1, G1 and B1 bands are used for one eye image, and R2, G2, B2 for the other eye. The human eye is largely insensitive to such fine spectral differences so this technique is able to generate full-color 3D images with only slight color differences between the two eyes.<ref>{{cite journal |title=Stereo projection using interference filters |journal=Stereoscopic Displays and Applications |year=2006 |first=Helmut |last=Jorke |author2=Fritz M. |editor5-first=Ian E |editor5-last=McDowall |editor4-first=Mark T |editor4-last=Bolas |editor3-first=John O |editor3-last=Merritt |editor2-first=Neil A |editor2-last=Dodgson |editor1-first=Andrew J |editor1-last=Woods |series=Stereoscopic Displays and Virtual Reality Systems XIII |volume=Proc. SPIE 6055 |page=148 |doi=10.1117/12.650348 |bibcode=2006SPIE.6055..148J |s2cid=59058512 |url=http://spie.org/x648.xml?product_id=650348 |access-date=November 19, 2008 |url-status = live|archive-url=https://web.archive.org/web/20131217064428/http://spie.org/x648.xml?product_id=650348 |archive-date=December 17, 2013 |url-access=subscription }}</ref>
 
The Omega 3D/[[Panavision 3D]] system also used this technology, though with a wider spectrum and more "teeth" to the "comb" (5 for each eye in the Omega/Panavision system). The use of more spectral bands per eye eliminates the need to color process the image, required by the Dolby system. Evenly dividing the visible spectrum between the eyes gives the viewer a more relaxed "feel" as the light energy and color balance is nearly 50-50. Like the Dolby system, the Omega system can be used with white or silver screens. But it can be used with either film or digital projectors, unlike the Dolby filters that are only used on a digital system with a color correcting processor provided by Dolby. The Omega/Panavision system also claims that their glasses are cheaper to manufacture than those used by Dolby.<ref>{{cite journal |title=Seeing is believing |journal=Cinema Technology |volume=24 |issue=1 |date=March 2011}}</ref> In June 2012 the Omega 3D/Panavision 3D system was discontinued by DPVO Theatrical, who marketed it on behalf of Panavision, citing "challenging global economic and 3D market conditions".<ref>{{cite web |url=http://www.dpvotheatrical.com/Home_Page.html |title=Home |access-date=April 3, 2012 |url-status = usurped|archive-url=https://web.archive.org/web/20120407125922/http://www.dpvotheatrical.com/Home_Page.html |archive-date=April 7, 2012}}</ref>
Although DPVO dissolved its business operations, Omega Optical continues promoting and selling 3D systems to non-theatrical markets. Omega Optical's 3D system contains projection filters and 3D glasses. In addition to the passive stereoscopic 3D system, Omega Optical has produced enhanced anaglyph 3D glasses. The Omega's red/cyan anaglyph glasses use complex metal oxide thin film coatings and high quality annealed glass optics.
 
== Viewing ==
[[File:3D-glasses.png|thumb|right|Red-green anaglyph glasses, with red for the right eye (unusual)]]
[[File:3d_loco.jpg|thumb|right|Red-cyan anaglyph of 1:8 scale [[Live steam]] locomotive
{{3D glasses}}]]
A pair of glasses, with filters of opposing colors, is worn to view an anaglyphic photo image. A red filter lens over the left eye allows graduations of red to cyan from within the anaglyph to be perceived as graduations of bright to dark. The cyan (blue/green) filter over the right eye conversely allows graduations of cyan to red from within the anaglyph to be perceived as graduations of bright to dark. Red and cyan color fringes in the anaglyph display represent the red and cyan color channels of the parallax-displaced left and right images. The viewing filters each cancel out opposing colored areas, including graduations of less pure opposing colored areas, to each reveal an image from within its color channel. Thus the filters enable each eye to see only its intended view from color channels within the single anaglyphic image. [[RG color models|Red-green]] glasses are also usable, but may give the viewer a more strongly colored view, since red and green are not [[complementary colors]].
 
=== Red sharpened anaglyph glasses ===
Simple paper uncorrected gel glasses, cannot compensate for the 250 nanometer difference in the wavelengths of the red-cyan filters. With simple glasses, the red filtered image is somewhat blurry, when viewing a close computer screen or printed image. The red retinal focus differs from the image through the cyan filter, which dominates the eyes' focusing. Better-quality molded acrylic glasses frequently employ a compensating differential [[diopter]] power (a [[Eyeglass prescription#Spherical lenses and spherical correction|spherical correction]]) to balance the red filter focus shift relative to the cyan, which reduces the innate softness and diffraction of red filtered light. Low-power reading glasses worn along with the paper glasses also sharpen the image noticeably.
 
The correction is only about 1/2 + diopter on the red lens. However, some people with corrective glasses are bothered by difference in lens diopters, as one image is a slightly larger magnification than the other. Though endorsed by many 3D websites, the diopter "fix" effect is still somewhat controversial. Some, especially the nearsighted, find it uncomfortable. There is about a 400% improvement in acuity with a molded diopter filter, and a noticeable improvement of contrast and blackness. The American [[Amblyopia]] Foundation uses this feature in their plastic glasses for school screening of children's vision, judging the greater clarity as a significant plus factor.
 
=== Anachrome filters ===
Plastic glasses, developed in recent years, provide both the diopter "fix" noted above, and a change in the cyan filter. The formula provides intentional "leakage" of a minimal (2%) percentage of red light with the conventional range of the filter. This assigns two-eyed "redness cues" to objects and details, such as lip color and red clothing, that are fused in the brain. Care must be taken, however, to closely overlay the red areas into near-perfect registration, or "ghosting" can occur. Anachrome formula lenses work well with black and white, but can provide excellent results when the glasses are used with conforming "anachrome friendly" images. The [[United States Geological Survey|US Geological Survey]] has thousands of these "conforming" full-color images, which depict the geology and scenic features of the [[National Park Service|U.S. National Park system]]. By convention, anachrome images try to avoid excess separation of the cameras and [[parallax]], thereby reducing the ghosting that the extra color bandwidth introduces to the images.
 
== Traditional anaglyph processing methods ==
{{multiple image |direction=horizontal |align=right |total_width=400
|image1=3-d anaglyph of Zagreb (2007).jpg |caption1=B&W anaglyph of [[Zagreb]] taken using one camera. Images were taken about {{convert|2|m|ft|frac=2|abbr=on}} apart to get the 3D effect. {{3D glasses}}
|image2=LGColorAnaglyphSceneMR.jpg |caption2=Color anaglyph taken using two cameras about {{convert|40|cm|in|round=5|abbr=on}} apart for enhanced depth effect. {{3D glasses}}
}}
 
One monochromatic method uses a stereo pair available as a digitized image, along with access to general-purpose image processing software. In this method, the images are run through a series of processes and saved in an appropriate transmission and viewing format such as [[JPEG]].
 
Several computer programs will create color anaglyphs without [[Adobe Photoshop]], or a traditional, more complex compositing method can be used with Photoshop. Using color information, it is possible to obtain reasonable (but not accurate) blue sky, green vegetation, and appropriate skin tones. Color information appears disruptive when used for brightly colored and/or high-contrast objects such as signs, toys, and patterned clothing when these contain colors that are close to red or cyan.
 
Only few color anaglyphic processes, e.g. interference filter systems used for [[Dolby 3D]], can reconstruct full-color 3D images. However, other [[stereo display]] methods can easily reproduce full-color photos or movies, e.g. [[active shutter 3D system|active shutter 3D]] or [[polarized 3D system]]s. Such processes allow better viewing comfort than most limited color anaglyphic methods. According to entertainment trade papers, [[3D film]]s had a revival in recent years and 3D is also used in [[3D TV|3D Television]].{{reltime|date=September 2023}}
 
=== Depth adjustment ===
{{multiple image |direction=vertical |align=left |total_width=400
|image1=TwinPeaks glyph th.png |caption1=Image as originally presented by [[NASA]] with foreground spilling from the frame. This is a two-color (red-cyan) anaglyph from the [[Mars Pathfinder]] mission. To view, use a red filter for the left eye and a cyan filter for the right eye. The distant mountain images are aligned, placing them at the screen, and the appearance in the lower right corner is confusing. {{3D glasses}}
|image2=TwinPeaksDepthAdjusted.jpg |caption2=Image adjusted so that most objects appear to be beyond the frame. The mountain images are now separated when viewed without the glasses. This follows the rule for a red left eye filter when distant objects are beyond the image plane: RRR-Red to Right Receding for dark objects on lighter background in the image as it appears without wearing the filters. {{3D glasses}}
}}
 
The suggested adjustment is applicable to any type of stereogram but is particularly appropriate when anaglyphed images are to be viewed on a computer screen or on printed matter.
 
Those portions of the left and right images that are coincident will appear to be at the surface of the screen. Depending upon the subject matter and the composition of the image it may be appropriate to make this align to something slightly behind the nearest point of the principal subject (as when imaging a portrait). This will cause the near points of the subject to "pop out" from the screen. For best effect, any portions of a figure to be imaged forward of the screen surface should not intercept the image boundary, as this can lead to a discomforting "amputated" appearance. It is of course possible to create a three-dimensional "pop out" frame surrounding the subject in order to avoid this condition.
[[Image:AnaglyphPopOutAdj.jpg|thumb|200px|Shelf edge at screen depth.]]
If the subject matter is a landscape, you may consider putting the frontmost object at or slightly behind the surface of the screen. This will cause the subject to be framed by the window boundary and recede into the distance. Once the adjustment is made, trim the picture to contain only the portions containing both left and right images. In the example shown above, the upper image appears (in a visually disruptive manner) to spill out from the screen, with the distant mountains appearing at the surface of the screen. In the lower modification of this image the red channel has been translated horizontally to bring the images of the nearest rocks into coincidence (and thus appearing at the surface of the screen) and the distant mountains now appear to recede into the image. This latter adjusted image appears more natural, appearing as a view through a window onto the landscape.
 
If the subject matter is a landscape, one may consider putting the frontmost object at or slightly behind the surface of the screen. This will cause the subject to be framed by the window boundary and recede into the distance. Once the adjustment is made, trim the picture to contain only the portions containing both left and right images. In the example, the upper image appears (in a visually disruptive manner) to spill out from the screen, with the distant mountains appearing at the surface of the screen. In the lower modification of this image the red channel has been translated horizontally to bring the images of the nearest rocks into coincidence (and thus appearing at the surface of the screen) and the distant mountains now appear to recede into the image. This latter adjusted image appears more natural, appearing as a view through a window onto the landscape.
[[Image:AbaglypMonochromeToy.jpg|thumb|200px|Monochrome version.]]
 
=== Scene composition ===
{{empty section|date=February 2022}}
In the toy images to the right, the shelf edge was selected as the point where images are to coincide and the toys were arranged so that only the central toy was projecting beyond the shelf. When the image is viewed the shelf edge appears to be at the screen, and the toy's feet and snout project toward the viewer, creating a "pop out" effect.
 
=== Dual purpose, 2D or 3D "compatible anaglyph" technique ===
==In comics==
Since the advent of the Internet, a variant technique has developed where the images are specially processed to minimize visible mis-registration of the two layers. This technique is known by various names, the most common, associated with diopter glasses, and warmer skin tones, is Anachrome. The technique allows most images to be used as large thumbnails, while the 3D information is encoded into the image with less parallax than conventional anaglyphs.
[[Image:Batman-anaglyph-3-d-glasses.jpg|left|framed|3-D Glasses distributed with special [[Batman]] [[comic book]]s between 1953 and 1964]]
These techniques have been used to produce 3-dimensional [[comic book]]s, mostly during the early 1950s, using carefully constructed line drawings printed in colors appropriate to the filter glasses provided. The material presented were typically short [[graphic novels]] of a war story, horror, or crime/detective nature - similar in content to some modern [[Manga|Japanese ''manga'']]. These genres were largely eliminated in the US by the rise of the [[Comics Code Authority]]. Anaglyphed images were of little interest for use in the remaining comics, which emphasized bright and colorful images, unsuited for use with the viewing and production methods available at the time, which were usually red-green rather than red-cyan.
 
== Modern Anaglyph Rendering Techniques ==
==In fine arts==
Anaglyphic images made with cameras used to be constructed by having the lens covered with the appropriate coloured filter. Modern video/image rendering programs use a similar technique to achieve the anaglyph effect. Modern anaglyphic rendering programs used to use simulated filters over the virtual cameras, for Red/Cyan anaglyphs the left camera blocking all but red light being perceived and the right blocking all but the blue and green light being received. This worked okay for creating colourful anaglyph images but the results were prone to [[Binocular rivalry|retinal rivalry]]
Some maintainers of internet web sites have added depth information to images of famous paintings, further processing these to produce color anaglyph images. [http://www.schudio.co.uk/ Chu], a [[Graffiti]] artist from the UK has created largescale, improvised, anaglyphic murals, most notably for the UK premiere of ''[[Donnie Darko]]''.
 
In 2001 Eric Dubois<ref>{{Cite web |title=Dubois, Eric |url=https://engineering.uottawa.ca/people/dubois-eric |access-date=2022-05-26 |website=Engineering |language=en}}</ref> released a paper titled 'A projection method to generate anaglyph stereo images'.<ref>{{Cite web |date=February 2001 |title=A projection method to generate anaglyph stereo images |url=https://www.researchgate.net/publication/3908713}}</ref> This paper described a method of filtering for anaglyph images that retained much of the colour and reduced ghosting and retinal rivalry The algorithm used to create this effect is called the least-squares algorithm. The result is a matrix that is applied over each virtual camera and forms a filter. His Matrix has been incorporated into many anaglyph programs such as StereoPhoto Maker<ref>{{Cite web |title=StereoPhoto Maker (English) |url=https://stereo.jpn.org/eng/stphmkr/ |access-date=2022-05-26 |website=stereo.jpn.org}}</ref> and threeJs's anaglyph effect.<ref>{{Cite web |title=three.js webgl - effects - anaglyph |url=https://threejs.org/examples/webgl_effects_anaglyph.html |access-date=2022-05-26 |website=threejs.org}}</ref><ref>{{Cite patent|number=9241153|title=United States Patent: 9241153 - Contrast adjusted anaglyph for reducing ghosting artifacts|gdate=January 19, 2016|invent1=Hui|invent2=SG|inventor1-first=Lucas|url=https://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/PTO/srchnum.htm&r=1&f=G&l=50&s1=9241153.PN.&OS=PN/9241153}}</ref>
==External links==
{{commonscat|Anaglyphs}}
* [http://www.opentutorial.com/Make_3d_images How to make Anaglyphs] - A step by step tutorial on how to make your own anaglyphs
* [http://wxs.ca/3d/howto.shtml How to make colour Anaglyphs] - An alternate method for making anaglyphs while retaining some of the colour information from the original image.
* [http://3dparks.wr.usgs.gov/ National Parks USGS], nearly 2000 3D images
* [http://dogfeathers.com/3d/ Mark Newobold's Stereo 3d Stuff] - A collection of anaglyphs and anaglyph resources
* [http://www.exploramuseum.de/ Explora Museum in Frankfurt/Main - Germany - Europe]
* [http://www.3d-museum.de/ 3D Museum in Dinkelsbühl - Germany - Europe]
* [http://www.somerset3d.co.uk Gallery - Anaglyphs of towns & villages in the county of Somerset in the UK]
* [http://multimedia.tbo.com/flash/iwojima3d/index.htm 3-D Stereo Photograph of Iwo Jima Flag-raising] - From The Tampa Tribune and TBO.com
* [http://www.flickr.com/groups/anaglyph/ Flickr Anaglyph Group]
* [http://stereo.jpn.org/eng/stphmkr/ Stereo Photo Maker] A free and easy-to-use program that assists in the creation of anaglyph images.
* [http://www.outline.be/quicktime/stjacques3d.html The church of Saint-Jacques (Liège in Belgium)] Color anaglyphical cubic QTVR
* Article about [http://vrm.vrway.com/issue10/COLOR_ANAGLYPHICAL_VR.html the first color anaglyphical cubic QuickTime VR panorama (panography by Alain Hamblenne)]
 
== Anaglyphic color channels ==
[[Category:Optical illusions]]
Anaglyph images may use any combination of color channels. However, if a stereoscopic image is to be pursued, the colors should be diametrically opposed. Impurities of color channel display, or of the viewing filters, allow some of the image meant for the other channel to be seen. This results in stereoscopic double imaging, also called ghosting. Color channels may be left-right reversed. Red/cyan is most common. magenta/green and blue/yellow are also popular. Red/green and red/blue enable monochromatic images, especially red/green. Many anaglyph makers purposely integrate impure color channels and viewing filters to enable better color perception, but this results in a corresponding degree of double imaging. Color channel brightness % of white: red-30/cyan-70, magenta-41/green-59 or especially blue-11/yellow-89), the lighter display channel may be darkened or the brighter viewing filter may be darkened to allow both eyes a balanced view. However the [[Pulfrich effect]] can be obtained from a light/dark filter arrangement. The color channels of an anaglyphic image require pure color display fidelity and corresponding viewing filter gels. The choice of ideal viewing filters is dictated by the color channels of the anaglyph to be viewed. Ghosting can be eliminated by ensuring a pure color display and viewing filters that match the display. [[Binocular rivalry|Retinal rivalry]] can be eliminated by the (ACB) 3-D ''Anaglyphic Contrast Balance'' method patented by{{clarify|date=March 2017|reason=Patented by who? The source doesn't say who.}}<ref>{{cite web |url=http://www.acb3d.com/whatisacb3d.html |title=What is (ACB) 3-D Anaglyph? |access-date=May 29, 2012 |url-status = live|archive-url=https://web.archive.org/web/20120510192200/http://www.acb3d.com/whatisacb3d.html |archive-date=May 10, 2012 }} Studio 555</ref> that prepares the image pair prior to color channeling in any color.
[[Category:3D imaging]]
 
{{Clear}}
[[de:Anaglyphenbild]]
{| class="wikitable" style="width:100%;"
[[fr:Anaglyphe]]
! style="width:10em;" | Scheme
[[it:Anaglifo]]
! colspan=2 | Left eye
[[pl:anaglif]]
! colspan=2 | Right eye
[[ru:Анаглиф]]
! Perceived color
[[vi:Kính màu 3 chiều]]
! style="width:50%;" | Description
|-
| '''[[RG color models|red-green]]'''
| pure red
| style="width:1.3em; background-color:#FF0000" | &nbsp;
| style="width:1.3em; background-color:#00FF00" | &nbsp;
| pure green
| monochrome
| The predecessor of red-cyan. Used for printed materials, e.g. books and comics.
|-
| '''red-blue'''
| pure red
| style="background-color:#FF0000" | &nbsp;
| style="background-color:#0000FF" | &nbsp;
| pure blue
| monochrome
| Some green-blue color perception. Often used for printed materials. Poor perception of red and inadequate perception of blue when watching LCD, or digital projector due to strong color separation.
|-
| '''red-cyan'''
| pure red
| style="background-color:#FF0000" | &nbsp;
| style="background-color:#00FFFF" | &nbsp;
| pure cyan; i.e., green&nbsp;+ blue
| color (poor reds, good greens)
| Good color perception of green and blue. No red is visible on digital media due to strong separation of red. This is most commonly used. Regular version (red channel has only the red third of the view) Half version (red channel is a red-tinted grayscale view. Less [[retinal rivalry]]).
|-
| '''anachrome'''
| dark red
| style="background-color:#CC0000" | &nbsp;
| style="background-color:#99CCFF" | &nbsp;
| cyan; i.e., green&nbsp;+ blue&nbsp;+ some red
| color (poor reds)
| A variant of red-cyan; left eye has dark red filter, right eye has a cyan filter leaking some red; better color perception, shows red hues with some ghosting.
|-
| '''mirachrome'''
| dark red, and lens
| style="background-color:#CC0000" | &nbsp;
| style="background-color:#99CCFF" | &nbsp;
| cyan; i.e., green&nbsp;+ blue&nbsp;+ some red
| color (poor reds)
| Same as anachrome, with addition of a weak positive correction lens on the red channel to compensate for the [[chromatic aberration]] soft focus of red.
|-
| '''Trioscopic'''
| pure green
| style="background-color:#00FF00" | &nbsp;
| style="background-color:#FF00FF" | &nbsp;
| pure{{nbsp}}magenta; i.e., red&nbsp;+ blue
| color (better reds, oranges and wider range of blues than red/cyan)
| Same principle as red-cyan, somewhat newer. Less chromatic aberration, as the red and blue in magenta brightness balance well with green. Poor perception of monochrome green on digital media due to strong color separation. Strong ghosting effect on contrast images.
|-
| '''[[ColorCode 3-D]]'''
| amber (red&nbsp;+ green&nbsp;+ neutral grey)
| style="background-color:#FFBF00" | &nbsp;
| style="background-color:#000099" | &nbsp;
| pure dark blue (and optional lens)
| color (near full-color perception)
| Also named yellow-blue, ochre-blue, or brown-blue. Newer system deployed in 2000s; better color rendering, but dark image, requires dark room or very bright image. Left filter darkened to equalize the brightness received by both eyes as the sensitivity to dark blue is poor. Older people may have problems perceiving the blue. Like in the mirachrome system, the chromatic aberration can be compensated with a weak negative correction lens (−0.7{{nbsp}}[[diopter]]) over the right eye.<ref>[http://nzphoto.tripod.com/sterea/anaglyphs_yb.html Yellow/Blue anaglyphs (ColorCode)<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20100425052941/http://nzphoto.tripod.com/sterea/anaglyphs_yb.html |date=April 25, 2010 }}</ref> Works best in the [[RG color space]]. The weak perception of the blue image may allow watching the movie without glasses and not seeing the disturbing double-image.<ref>{{cite web |url=http://www.3dstore.nl/product_info.php?products_id=68 |title=3dstore<!-- Bot generated title --> |website=3dstore.nl |access-date=May 7, 2018 |url-status = dead|archive-url=https://web.archive.org/web/20100525031303/http://www.3dstore.nl/product_info.php?products_id=68 |archive-date=May 25, 2010 }}</ref><!-- commercial link;
todo: find a better mention of the same and source it from there -->
|-
| '''magenta-cyan'''
| pure{{nbsp}}magenta; i.e., red&nbsp;+ blue
| style="background-color:#FF00FF" | &nbsp;
| style="background-color:#00FFFF" | &nbsp;
| pure cyan; i.e., green&nbsp;+ blue
| color (better than red-cyan)
| Experimental; similar to red-cyan, better brightness balance of the color channels and the same retinal rivalry. Blue channel is blurred horizontally by the amount equal to the average parallax, and visible to both eyes; the blurring prevents eyes from using the blue channel to construct stereoscopic image and therefore prevents ghosting, while supplying both eyes with color information.<ref>{{cite web |url=http://www.divideconcept.net/papers/MCA-RL09.pdf |title=Archived copy |access-date=June 6, 2010 |url-status = live|archive-url=https://web.archive.org/web/20100821221626/http://www.divideconcept.net/papers/MCA-RL09.pdf |archive-date=August 21, 2010 }} {{circular reference|date=July 2022}}.</ref>
|}
 
In theory, under trichromatic principles, it is possible to introduce a limited amount of multiple-perspective capability (a technology not possible with polarization schemes). This is done by overlapping three images instead of two, in the sequence of green, red, blue. Viewing such an image with red-green glasses would give one perspective, while switching to blue-red would give a slightly different one. In practice, this remains elusive as some blue is perceived through green gel and most green is perceived through blue gel. It is also theoretically possible to incorporate [[rod cell]]s, which optimally perform at a dark cyan color, in well-optimized [[mesopic vision]], to create a fourth filter color and yet another perspective; however, this has not yet been demonstrated, nor would most televisions be able to process such [[tetrachromacy|tetrachromatic]] filtering.
 
== Applications ==
On April 1, 2010, [[Google]] launched a feature in [[Google Street View]] that shows anaglyphs rather than regular images, allowing users to see the streets in 3D.
 
=== Home entertainment ===
{{Unreferenced section|date=April 2013}}
Disney Studios released ''[[Hannah Montana & Miley Cyrus: Best of Both Worlds Concert]]'' in August 2008, its first anaglyph 3D [[Blu-ray Disc]]. This was shown on the [[Disney Channel]] with red-cyan paper glasses in July 2008.
 
However, on Blu-ray Disc anaglyph techniques have more recently been supplanted by the [[Blu-ray Disc#Blu-ray 3D|Blu-ray 3D]] format, which uses [[Multiview Video Coding]] (MVC) to encode full stereoscopic images. Though Blu-ray 3D does not require a specific display method, and some Blu-ray 3D software players (such as [[Arcsoft TotalMedia Theatre]]) are capable of anaglyphic playback, most Blu-ray 3D players are connected via [[HDMI#Version 1.4|HDMI 1.4]] to [[3D television]]s and other [[3D display]]s using more advanced stereoscopic display methods, such as [[alternate-frame sequencing]] (with [[Liquid crystal shutter glasses|active shutter glasses]]) or [[film-type patterned retarder|FPR]] [[Polarization (waves)|polarization]] (with the same [[Polarized 3D glasses|passive glasses]] as [[RealD Cinema|RealD]] [[3D film|theatrical 3D]]).
 
=== Comics ===
<!-- Commented out: [[File:Batman-anaglyph-3-d-glasses.jpg|left|framed|3-D Glasses distributed with special [[Batman]] [[comic book]]s between 1953 and 1964]] -->
 
These techniques have been used to produce 3-dimensional [[comic book]]s, mostly during the early 1950s, using [[Three Dimensional E.C. Classics#Three-dimensional comics|carefully constructed line drawings]] printed in colors appropriate to the filter glasses provided. The material presented were from a wide variety of genres, including war, horror, crime, and superhero. Anaglyphed comics were far more difficult to produce than normal comics, requiring each panel to be drawn multiple times on layers of acetate. While the first 3D comic in 1953 sold over two million copies, by the end of the year sales had bottomed out, though 3D comics have continued to be released irregularly up until the present day.<ref>[http://www.twomorrows.com/media/AlterEgo115Preview.pdf Zone, Ray. "The 3-D-T's", ''Alter Ego'' #113, March 2013, retrieved March 3, 2014] {{webarchive|url=https://web.archive.org/web/20140304034056/http://www.twomorrows.com/media/AlterEgo115Preview.pdf |date=March 4, 2014 }}</ref>
 
=== Science and mathematics ===
{{multiple image |direction=horizontal |align=right |total_width=500 |perrow=3 |footer={{3D glasses}}
|image1=Anaglyph example graph.png |caption1=The single valued function of two variables <math>z(x,y)=x^2+y^3</math> with the function value displayed as the height
|image2=Elephant on Mars anaglyph.jpg |caption2=Anaglyph by the [[Mars Reconnaissance Orbiter]]{{'s}} [[HiRISE]] camera highlighting Martian lava terrain that looks like an elephant
|image3=Anaglyph image of a protein DHFR.png |caption3=Anaglyph image of the protein [[DHFR]]
}}
 
Three-dimensional display can also be used to display scientific data sets, or to illustrate mathematical functions. Anaglyph images are suitable both for paper presentation, and moving video display (see neuroimage related paper<ref>{{cite journal |last1=Rojas |first1=G.M. |last2=Galvez |first2=M. |last3=Vega Potler |first3=N. |last4=Craddock |first4=R.C. |last5=Margulies |first5=D.S. |last6=Castellanos |first6=F.X. |last7=Milham |first7=M.P. |year=2014 |title=Stereoscopic three-dimensional visualization applied to multimodal brain images: clinical applications and a functional connectivity atlas |journal=Front. Neurosci. |volume=8 |issue=328 |page=328 |doi=10.3389/fnins.2014.00328|pmc=4222226 |pmid=25414626|doi-access=free }}</ref>). They can easily be included in science books, and viewed with cheap anaglyph glasses.
 
Anaglyphy (including, among others, aerial, telescopic, and microscopic images) is being applied to scientific research, popular science, and higher education.<ref>{{cite journal |last=Hortolà |first=P. |year=2009 |title=Using digital anaglyph to improve the relief effect of SEM micrographs of bloodstains |journal=Micron |volume=40 |issue=3 |pages=409–412 |doi=10.1016/j.micron.2008.09.008|pmid=19038551 }}</ref>
 
Also, chemical structures, particularly for large systems, can be difficult to represent in two dimensions without omitting geometric information. Therefore, most chemistry computer software can output anaglyph images, and some chemistry textbooks include them.
 
Today, there are more advanced solutions for 3D imaging available, like [[shutter glasses]] together with fast monitors. These solutions are already extensively used in science. Still, anaglyph images provide a cheap and comfortable way to view scientific visualizations.
 
== See also ==
* [[Holography]]
* [[Autostereogram]]
* [[Phantogram (optical illusion)]]
* [[Pulfrich effect]]
* [[Vectograph]]
* [[Charles Wheatstone#Optics|Wheatstone viewer]]
 
== References ==
{{Reflist}}
 
== External links ==
{{Commons category|Anaglyphs}}
* [https://web.archive.org/web/20110520054853/http://www.physics.gla.ac.uk/Optics/play/TIM/ TIM] - Online raytracer that also generates anaglyphs (for red/blue glasses) and autostereograms
* [http://www.3dstreaming.org 3D STEREO PORTAL Videos & Photos Collection] from the World
* [https://fliiby.com/folder/3lael7/ 3D Anaglyph red-cyan] {{Webarchive|url=https://web.archive.org/web/20151208195905/https://fliiby.com/folder/3lael7/ |date=December 8, 2015 }}
* [https://brooklynstereographic.com/anaglyph-gallery/ Anaglyph Gallery] at Brooklyn Stereography featuring hundreds of red-cyan anaglyphs
* [https://www.joelfletcher.com/creative-process/?post=3d-anaglyph-technique 3-D Anaglyph Technique]
* [https://www.joelfletcher.com/3d-gallery/ Amazing 3-D Stereo Anaglyph Photos] featuring various unusual subjects
* [http://www.sparetimelabs.com/animato/animato/3d/3d2.html Making a 3-D anaglyph movie with two 16mm cameras]
* [https://stereoscopictures.com/3d-pictures/anaglyph/2024/anaglyphs/ Achim Bahr: Anaglyphs]
{{Stereoscopy}}
 
{{DEFAULTSORT:Anaglyph Image}}
 
[[Category:1853 introductions]]
[[Category:Stereoscopic photography]]
[[Category:3D imaging]]
[[Category:Articles containing video clips]]