`
`Stereoscopy - Wikipedia, the free encyclopedia
`
`Stereoscopy
`
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`Stereoscopy (also called stereoscopics or 3D imaging) is a technique for creating
`or enhancing the illusion of depth in an image by means of stereopsis for binocular
`vision. The word stereoscopy derives from the Greek "στερεός" (stereos), "firm,
`solid"[2] + "σκοπέω" (skopeō), "to look", "to see".[3]
`
`Most stereoscopic methods present two offset images separately to the left and right
`eye of the viewer. These two-dimensional images are then combined in the brain to
`give the perception of 3D depth. This technique is distinguished from 3D displays
`that display an image in three full dimensions, allowing the observer to increase
`information about the 3-dimensional objects being displayed by head and eye
`movements.
`
`Contents
`
`1 Background
`1.1 Visual requirements
`2 Side-by-side
`2.1 Freeviewing
`2.2 Autostereogram
`2.3 Stereoscope and stereographic cards
`2.4 Transparency viewers
`2.5 Head-mounted displays
`2.6 Virtual retinal displays
`3 3D viewers
`3.1 Active
`3.1.1 Shutter systems
`3.2 Passive
`3.2.1 Polarization systems
`3.2.2 Interference filter systems
`3.2.3 Color anaglyph systems
`3.2.4 Chromadepth system
`3.2.5 Pulfrich method
`3.2.6 Over/under format
`4 Other display methods without viewers
`4.1 Autostereoscopy
`4.1.1 Holography
`4.1.2 Volumetric displays
`4.1.3 Integral imaging
`4.2 Wiggle stereography
`5 Stereo photography techniques
`
`Pocket stereoscope with original test
`image. Used by military to examine
`stereoscopic pairs of aerial
`photographs.
`
`View of Boston, c. 1860; an early
`stereoscopic card for viewing a scene
`from nature
`
`Kaiserpanorama consisted of a multi-
`station viewing apparatus and sets of
`stereo slides. Patented by A.
`Fuhrmann around 1890.[1]
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`Stereoscopy - Wikipedia, the free encyclopedia
`5.1 Film photography
`5.2 Digital photography
`5.3 Digital stereo bases (baselines)
`6 Base line selection
`6.1 Longer base line for distant objects "Hyper Stereo"
`6.1.1 Limitations of hyperstereo
`6.1.2 A practical example
`6.2 Shorter baseline for ultra closeups "Macro stereo"
`6.3 Baseline tailored to viewing method
`6.4 Variable base for "geometric stereo"
`6.4.1 Precise stereoscopic baseline calculation methods
`6.4.2 Multi-rig stereoscopic cameras
`7 Stereo Window
`8 Bibliography
`8.1 Footnotes
`8.2 References
`8.3 Sources
`9 External links
`
`Background
`
`Company of ladies watching
`stereoscopic photographs, painting by
`Jacob Spoel, before 1868. A very
`early depiction of people using a
`stereoscope.
`
`Stereoscopy creates the illusion of three-dimensional depth from given two-dimensional images. Human vision, including the
`perception of depth, is a complex process which only begins with the acquisition of visual information taken in through the
`eyes; much processing ensues within the brain, as it strives to make intelligent and meaningful sense of the raw information
`provided. One of the very important visual functions that occur within the brain as it interprets what the eyes see is that of
`assessing the relative distances of various objects from the viewer, and the depth dimension of those same perceived objects.
`The brain makes use of a number of cues to determine relative distances and depth in a perceived scene, including:[4]
`
`Stereopsis
`Accommodation of the eye
`Overlapping of one object by another
`Subtended visual angle of an object of known size
`Linear perspective (convergence of parallel edges)
`Vertical position (objects higher in the scene generally tend to be perceived as further away)
`Haze, desaturation, and a shift to bluishness
`Change in size of textured pattern detail
`
`(All the above cues, with the exception of the first two, are present in traditional two-dimensional images such as paintings,
`photographs, and television.)
`
`Stereoscopy is the production of the illusion of depth in a photograph, movie, or other two-dimensional image by presenting a
`slightly different image to each eye, and thereby adding the first of these cues (stereopsis) as well. Both of the 2D offset images
`are then combined in the brain to give the perception of 3D depth. It is important to note that since all points in the image focus
`at the same plane regardless of their depth in the original scene, the second cue, focus, is still not duplicated and therefore the
`illusion of depth is incomplete. There are also primarily two effects of stereoscopy that are unnatural for the human vision: first,
`the mismatch between convergence and accommodation, caused by the difference between an object's perceived position in
`front of or behind the display or screen and the real origin of that light and second, possible crosstalk between the eyes, caused
`by imperfect image separation by some methods.
`
`Although the term "3D" is ubiquitously used, it is also important to note that the presentation of dual 2D images is distinctly
`different from displaying an image in three full dimensions. The most notable difference is that, in the case of "3D" displays, the
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`different from displaying an image in three full dimensions. The most notable difference is that, in the case of "3D" displays, the
`observer's head and eye movement will not increase information about the 3-dimensional objects being displayed. Holographic
`displays or volumetric display are examples of displays that do not have this limitation. Similar to the technology of sound
`reproduction, in which it is not possible to recreate a full 3-dimensional sound field merely with two stereophonic speakers, it is
`likewise an overstatement of capability to refer to dual 2D images as being "3D". The accurate term "stereoscopic" is more
`cumbersome than the common misnomer "3D", which has been entrenched after many decades of unquestioned misuse.
`Although most stereoscopic displays do not qualify as real 3D display, all real 3D displays are also stereoscopic displays
`because they meet the lower criteria as well.
`
`Most 3D displays use this stereoscopic method to convey images. It was first invented by Sir Charles Wheatstone in
`1838.[5][6]
`
`Wheatstone originally used his stereoscope (a rather bulky device)[7] with drawings
`because photography was not yet available, yet his original paper seems to foresee
`the development of a realistic imaging method:[8]
`
`For the purposes of illustration I have employed only outline figures, for had
`either shading or colouring been introduced it might be supposed that the
`effect was wholly or in part due to these circumstances, whereas by leaving
`them out of consideration no room is left to doubt that the entire effect of
`relief is owing to the simultaneous perception of the two monocular
`projections, one on each retina. But if it be required to obtain the most faithful
`resemblances of real objects, shadowing and colouring may properly be employed to heighten the effects. Careful
`attention would enable an artist to draw and paint the two component pictures, so as to present to the mind of the
`observer, in the resultant perception, perfect identity with the object represented. Flowers, crystals, busts, vases,
`instruments of various kinds, &c., might thus be represented so as not to be distinguished by sight from the real
`objects themselves.[5]
`
`Wheatstone mirror stereoscope
`
`Stereoscopy is used in photogrammetry and also for entertainment through the production of stereograms. Stereoscopy is
`useful in viewing images rendered from large multi-dimensional data sets such as are produced by experimental data. An early
`patent for 3D imaging in cinema and television was granted to physicist Theodor V. Ionescu in 1936. Modern industrial three-
`dimensional photography may use 3D scanners to detect and record three-dimensional information.[9] The three-dimensional
`depth information can be reconstructed from two images using a computer by corresponding the pixels in the left and right
`images (e.g.,[10]). Solving the Correspondence problem in the field of Computer Vision aims to create meaningful depth
`information from two images.
`
`Visual requirements
`
`Anatomically, there are 3 levels of binocular vision required to view stereo images:
`
`1. Simultaneous perception
`2. Fusion (binocular 'single' vision)
`3. Stereopsis
`
`These functions develop in early childhood. Some people who have strabismus disrupt the development of stereopsis, however
`orthoptics treatment can be used to improve binocular vision. A person's stereoacuity determines the minimum image disparity
`they can perceive as depth. It is believed that approximately 12% of people are unable to properly see 3D images, due to a
`variety of medical conditions.[11][12] According to another experiment up to 30% of people have very weak stereoscopic
`vision preventing them from depth perception based on stereo disparity. This nullifies or greatly decreases immersion effects of
`stereo to them.[13]
`Side-by-side
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`Traditional stereoscopic photography consists of creating a 3D illusion starting from a pair of 2D images, a stereogram. The
`easiest way to enhance depth perception in the brain is to provide the eyes of the
`viewer with two different images, representing two perspectives of the same object,
`with a minor deviation equal or nearly equal to the perspectives that both eyes
`naturally receive in binocular vision.
`
`If eyestrain and distortion are to be avoided, each of the two 2D images preferably
`should be presented to each eye of the viewer so that any object at infinite distance
`seen by the viewer should be perceived by that eye while it is oriented straight
`ahead, the viewer's eyes being neither crossed nor diverging. When the picture
`contains no object at infinite distance, such as a horizon or a cloud, the pictures
`should be spaced correspondingly closer together.
`
`"The early bird catches the worm"
`Stereograph published in 1900 by
`North-Western View Co. of Baraboo,
`Wisconsin, digitally restored.
`
`The principal advantages of side-by-side viewers is that there is no diminution of brightness so images may be presented at
`very high resolution and in full spectrum color. The side-by-side method is simple to create. Little or no additional image
`processing is required. Under some circumstances, such as when a pair of images is presented for crossed or parallel eye
`viewing, no device or additional optical equipment is needed. But it can be difficult or uncomfortable to view without optical
`aids.
`
`Freeviewing
`
`Freeviewing is viewing a side-by-side image without using a viewer.[14]
`
`Two methods are available to freeview:[15][16]
`
`The parallel view method uses two images not more than 65mm between
`corresponding image points; this is the average distance between the two
`eyes. The viewer looks through the image while keeping the vision parallel;
`this can be difficult with normal vision since eye focus and binocular
`convergence normally work together.
`The cross-eyed view method uses the right and left images exchanged and
`views the images cross-eyed with the right eye viewing the left image and
`vice-versa. Prismatic, self-masking glasses are now being used by cross-view
`advocates. These reduce the degree of convergence and allow large images
`to be displayed.
`
`Autostereogram
`
`Main article: Autostereogram
`
`Printable cross eye viewer.
`
`An autostereogram is a single-image stereogram (SIS), designed to create the visual illusion of a three-dimensional (3D) scene
`within the human brain from an external two-dimensional image. In order to perceive 3D shapes in these autostereograms, one
`must overcome the normally automatic coordination between focusing and vergence.
`
`Stereoscope and stereographic cards
`
`Main article: Stereoscope
`
`The stereoscope is essentially an instrument in which two photographs of the same object, taken from slightly different angles,
`are simultaneously presented, one to each eye. A simple stereoscope is limited in the size of the image that may be used. A
`more complex stereoscope uses a pair of horizontal periscope-like devices, allowing the use of larger images that can present
`more detailed information in a wider field of view.
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`more detailed information in a wider field of view.
`
`Transparency viewers
`
`Main article: Slide viewer#Stereo slide viewer
`
`Pairs of stereo views are printed on translucent film which is then mounted around
`the edge of a cardboard disk, images of each pair being diametrically opposite. An
`advantage offered by transparency viewing is that a wider field of view may be
`presented since images, being illuminated from the rear, may be placed much closer
`to the lenses. The practice of viewing film-based transparencies in stereo via a
`viewer dates to at least as early as 1931, when Tru-Vue began to market filmstrips
`that were fed through a handheld device made from Bakelite. In the 1940s, a
`modified and miniaturized variation of this technology was introduced as the View-
`Master. Other key companies that developed and marketed stereoscopic viewers
`and cards include Bruguiere, Lestrade and ROMO - Robert Mouzillat.
`
`Head-mounted displays
`
`Main article: Head-mounted display
`
`The user typically wears a helmet or glasses with two small LCD or OLED displays
`with magnifying lenses, one for each eye. The technology can be used to show
`stereo films, images or games, but it can also be used to create a virtual display.
`Head-mounted displays may also be coupled with head-tracking devices, allowing
`the user to "look around" the virtual world by moving their head, eliminating the need
`for a separate controller. Performing this update quickly enough to avoid inducing
`nausea in the user requires a great amount of computer image processing. If six axis
`position sensing (direction and position) is used then wearer may move about within
`the limitations of the equipment used. Owing to rapid advancements in computer
`graphics and the continuing miniaturization of video and other equipment these
`devices are beginning to become available at more reasonable cost.
`
`A View-Master Model E of the 1950s
`
`An HMD with a separate video source
`displayed in front of each eye to
`achieve a stereoscopic effect
`
`Head-mounted or wearable glasses may be used to view a see-through image
`imposed upon the real world view, creating what is called augmented reality. This is done by reflecting the video images
`through partially reflective mirrors. The real world view is seen through the mirrors' reflective surface. Experimental systems
`have been used for gaming, where virtual opponents may peek from real windows as a player moves about. This type of
`system is expected to have wide application in the maintenance of complex systems, as it can give a technician what is
`effectively "x-ray vision" by combining computer graphics rendering of hidden elements with the technician's natural vision.
`Additionally, technical data and schematic diagrams may be delivered to this same equipment, eliminating the need to obtain
`and carry bulky paper documents.
`
`Augmented stereoscopic vision is also expected to have applications in surgery, as it allows the combination of radiographic
`data (CAT scans and MRI imaging) with the surgeon's vision.
`
`Virtual retinal displays
`
`Main article: Virtual retinal display
`
`A virtual retinal display (VRD), also known as a retinal scan display (RSD) or retinal projector (RP), not to be confused with a
`"Retina Display", is a display technology that draws a raster display (like a television) directly onto the retina of the eye. The
`user sees what appears to be a conventional display floating in space in front of them.
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`3D viewers
`
`There are two categories of 3D viewer technology, active and passive. Active
`viewers have electronics which interact with a display.
`
`Active
`
`Shutter systems
`
`Main article: Active shutter 3D system
`
`A Shutter system works by openly presenting the image intended for the left eye
`while blocking the right eye's view, then presenting the right-eye image while
`blocking the left eye, and repeating this so rapidly that the interruptions do not
`interfere with the perceived fusion of the two images into a single 3D image. It
`generally uses liquid crystal shutter glasses. Each eye's glass contains a liquid crystal
`layer which has the property of becoming dark when voltage is applied, being
`otherwise transparent. The glasses are controlled by a timing signal that allows the
`glasses to alternately darken over one eye, and then the other, in synchronization
`with the refresh rate of the screen.
`
`Passive
`
`Polarization systems
`
`Main article: Polarized 3D system
`
`A pair of LCD shutter glasses used to
`view XpanD 3D films. The thick
`frames conceal the electronics and
`batteries.
`
`RealD circular polarized glasses
`
`To present stereoscopic pictures, two images are projected superimposed onto the same screen through polarizing filters or
`presented on a display with polarized filters. For projection, a silver screen is used so that polarization is preserved. The
`viewer wears low-cost eyeglasses which also contain a pair of opposite polarizing filters. As each filter only passes light which
`is similarly polarized and blocks the opposite polarized light, each eye only sees one of the images, and the effect is achieved.
`
`Interference filter systems
`
`Main article: Anaglyph 3D#Interference filter systems
`
`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. It
`is also known as spectral comb filtering or wavelength multiplex visualization or super-anaglyph. Dolby 3D uses this
`principle. The Omega 3D/Panavision 3D system has also used an improved version of this technology[17] 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″.[18] 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.
`
`Color anaglyph systems
`
`Main article: Anaglyph 3D
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`Anaglyph 3D is the name given to the stereoscopic 3D effect achieved by means of 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 for each eye. When viewed through the "color-coded" "anaglyph glasses", each of the two images reaches
`one eye, revealing an integrated stereoscopic image. The visual cortex of the brain fuses this into perception of a three
`dimensional scene or composition.
`
`Chromadepth system
`
`Main article: ChromaDepth
`
`The ChromaDepth procedure of American Paper Optics is based on the fact that
`with a prism, colors are separated by varying degrees. The ChromaDepth
`eyeglasses contain special view foils, which consist of microscopically small prisms.
`This causes the image to be translated a certain amount that depends on its color. If
`one uses a prism foil now with one eye but not on the other eye, then the two seen
`pictures – depending upon color – are more or less widely separated. The brain
`produces the spatial impression from this difference. The advantage of this
`technology consists above all of the fact that one can regard ChromaDepth pictures
`also without eyeglasses (thus two-dimensional) problem-free (unlike with two-color
`anaglyph). However the colors are only limitedly selectable, since they contain the
`depth information of the picture. If one changes the color of an object, then its
`observed distance will also be changed.[citation needed]
`
`Anaglyph 3D glasses
`
`ChromaDepth glasses with prism-like
`film
`
`Pulfrich method
`
`Main article: Pulfrich effect
`
`The Pulfrich effect is based on the phenomenon of the human eye processing images
`more slowly when there is less light, as when looking through a dark lens. Because
`the Pulfrich effect depends on motion in a particular direction to instigate the illusion
`of depth, it is not useful as a general stereoscopic technique. For example, it cannot
`be used to show a stationary object apparently extending into or out of the screen;
`similarly, objects moving vertically will not be seen as moving in depth. Incidental
`movement of objects will create spurious artifacts, and these incidental effects will be
`seen as artificial depth not related to actual depth in the scene.
`
`Over/under format
`
`KMQ stereo prismatic viewer with
`openKMQ plastics extensions
`
`Stereoscopic viewing is achieved by placing an image pair one above one another. Special viewers are made for over/under
`format that tilt the right eyesight slightly up and the left eyesight slightly down. The most common one with mirrors is the View
`Magic. Another with prismatic glasses is the KMQ viewer.[19] A recent usage of this technique is the openKMQ project.[20]
`Other display methods without viewers
`Autostereoscopy
`
`Main article: Autostereoscopy
`
`Autostereoscopic display technologies use optical components in the display, rather than worn by the user, to enable each eye
`to see a different image. Because headgear is not required, it is also called "glasses-free 3D". The optics split the images
`directionally into the viewer's eyes, so the display viewing geometry requires limited head positions that will achieve the
`stereoscopic effect. Automultiscopic displays provide multiple views of the same scene, rather than just two. Each view is
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`stereoscopic effect. Automultiscopic displays provide multiple views of the same scene, rather than just two. Each view is
`visible from a different range of positions in front of the display. This allows the viewer to move left-right in front of the display
`and see the correct view from any position. The technology includes two broad classes of displays: those that use head-
`tracking to ensure that each of the viewer's two eyes sees a different image on the
`screen, and those that display multiple views so that the display does not need to
`know where the viewers' eyes are directed. Examples of autostereoscopic displays
`technology include lenticular lens, parallax barrier, volumetric display, holography
`and light field displays.
`
`Holography
`
`Main articles: Holography and Computer Generated Holography
`
`Research into holographic displays has produced devices which are able to create a
`light field identical to that which would emanate from the original scene, with both
`horizontal and vertical parallax across a large range of viewing angles. The effect is
`similar to looking through a window at the scene being reproduced; this may make
`CGH the most convincing of the 3D display technologies, but as yet the large
`amounts of calculation required to generate a detailed hologram largely prevent its
`application outside of the laboratory.
`
`Volumetric displays
`
`Main article: Volumetric display
`
`Volumetric displays use some physical mechanism to display points of light within a
`volume. Such displays use voxels instead of pixels. Volumetric displays include
`multiplanar displays, which have multiple display planes stacked up, and rotating
`panel displays, where a rotating panel sweeps out a volume.
`
`Other technologies have been developed to project light dots in the air above a
`device. An infrared laser is focused on the destination in space, generating a small
`bubble of plasma which emits visible light.
`
`Integral imaging
`
`Main article: Integral imaging
`
`The Nintendo 3DS uses parallax
`barrier autostereoscopy to display a
`3D image.
`
`Laser plasma volumetric display
`
`Integral imaging is an autostereoscopic or multiscopic 3D display, meaning that it displays a 3D image without the use of
`special glasses on the part of the viewer. It achieves this by placing an array of microlenses (similar to a lenticular lens) in front
`of the image, where each lens looks different depending on viewing angle. Thus rather than displaying a 2D image that looks
`the same from every direction, it reproduces a 4D light field, creating stereo images that exhibit parallax when the viewer
`moves.
`
`Wiggle stereography
`
`Main article: Wiggle stereoscopy
`
`Wiggle stereoscopy is an image display technique achieved by quickly alternating display of left and right sides of a stereogram.
`Found in animated GIF format on the web. Online examples are visible in the New-York Public Library stereogram collection
`(http://stereo.nypl.org/create). The technique is also known as "Piku-Piku".[21]
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`Stereo photography techniques
`
`Film photography
`
`It is necessary to take two photographs for a stereoscopic image. This can be done
`with two cameras, with one camera moved quickly to two positions, or with a
`stereo camera incorporating two or more side-by-side lenses.
`
`In the 1950s, stereoscopic photography regained popularity when a number of
`manufacturers began introducing stereoscopic cameras to the public. The new
`cameras were developed to use 135 film, which had gained popularity after the
`close of World War II. Many of the conventional cameras used the film for 35 mm
`transparency slides, and the new stereoscopic cameras utilized the film to make
`stereoscopic slides. The Stereo Realist camera was the most popular, and its 5P
`picture format became a standard. The stereoscopic cameras were marketed with
`special viewers that allowed for the use of such slides. With these cameras the
`public could easily create their own stereoscopic memories. Although their
`popularity has waned, some of these cameras are still in use today.
`
`The 1980s saw a minor revival of stereoscopic photography extent when point-and-
`shoot stereo cameras were introduced. Most of these cameras suffered from poor
`optics and plastic construction, and were designed to produce lenticular prints, a
`format which never gained wide acceptance, so they never gained the popularity of
`the 1950s stereo cameras.
`
`Digital photography
`
`The beginning of the 21st century marked the coming of the age of digital
`photography. Stereo lenses were introduced which could turn an ordinary film
`camera into a stereo camera by using a special double lens to take two images and
`direct them through a single lens to capture them side by side on the film. Although
`current digital stereo cameras cost hundreds of dollars,[22] cheaper models also
`exist, for example those produced by the company Loreo. It is also possible to
`create a twin camera rig, together with a "shepherd" device to synchronize the
`shutter and flash of the two cameras. By mounting two cameras on a bracket,
`spaced a bit, with a mechanism to make both take pictures at the same time. Newer
`cameras are even being used to shoot "step video" 3D slide shows with many
`pictures almost like a 3D motion picture if viewed properly. A modern camera can
`take ten pictures per second, with images that greatly exceed HDTV resolution.
`
`The Stereo Realist, which defined a
`new stereo format.
`
`Sputnik stereo camera (Soviet Union,
`1960s). Although there are three
`lenses present, only the lower two are
`used for the photograph – the third
`lens serves as a viewfinder for
`composition. The Sputnik produces
`two side-by-side square images on
`120 film.
`
`If anything is in motion within the field of view, it is necessary to take both images at once, either through use of a specialized
`two-lens camera, or by using two identical cameras, operated as close as possible to the same moment.
`
`A single camera can also be used if the subject remains perfectly still (such as an object in a museum display). Two exposures
`are required. The camera can be moved on a sliding bar for offset, or with practice, the photographer can simply shift the
`camera while holding it straight and level. This method of taking stereo photos is sometimes referred to as the "Cha-Cha" or
`"Rock and Roll" method.[23] It is also sometimes referred to as the "astronaut shuffle" because it was used to take stereo
`pictures on the surface of the moon using normal monoscopic equipment.[24]
`
`For the most natural looking stereo most stereographers move the camera about 65mm or the distance between the eyes,[25]
`but some experiment with other distances. A good rule of thumb is to shift sideways 1/30th of the distance to the closest
`subject for 'side by side' display, or just 1/60th if the image is to be also used for color anaglyph or anachrome image display.
`For example, when enhanced depth beyond natural vision is desired and a photo of a person in front of a house is being taken,
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`For example, when enhanced depth beyond natural vision is desired and a photo of a person in front of a house is being taken,
`and the person is thirty feet away, then the camera should be moved 1 foot between shots.[25]
`
`The stereo effect is not significantly diminished by slight pan or rotation between images. In fact slight rotation inwards (also
`called 'toe in') can be beneficial. Bear in mind that both images should show the same objects in the scene (just from different
`angles) – if a tree is on the edge of one image but out of view in the other image, then it will appear in a ghostly, semi-
`transparent way to the viewer, which is distracting and uncomfortable. Therefore, the images are cropped so they completely
`overlap, or the cameras 'toed-in' so that the images completely overlap without having to discard any of the images. However,
`too much 'toe-in' can cause 'keystoning' and eye strain for reasons best described here.[26]
`
`Digital stereo bases (baselines)
`
`There are different cameras with different stereobase (distance between the two camera lenses) in the not professional market
`of 3D digital cameras used for video and also for stills:
`
`10 mm Panasonic 3 D Lumix H-FT012 lens (for the GH2, GF2, GF3, GF5 cams and also for the hybrid W8 cam).
`
`12 mm Praktica and Medion 3D (two clones of the DXG-5D8 cam).
`
`20 mm Sony Blogie 3D.
`
`23 mm Loreo 3D Macro lens.
`
`25 mm LG Optimus 3D and LG Optimus 3D MAX smartphones and the close-up macro adapter for the W1 and W3 Fujifilm
`cams.
`
`28 mm Sharp Aquos SH80F smartphone and the Toshiba Camileo z100 camcorder.
`
`30 mm Panasonic 3D1 camera.
`
`32 mm HTC EVO 3D smartphone.
`
`35 mm JVC TD1, DXG-5G2V and Vivitar 790 HD (only for anagliph stills and video) camcorders.
`
`40 mm Aiptek I2, Aiptek IS2, Aiptek IH3 and Viewsonic 3D cams.
`
`50 mm Loreo for full frame cams, and the 3D FUN cam of 3dInlife.
`
`55 mm SVP dc-3D-80 cam (parallel & anagliph, stills & video).
`
`60 mm Vivitar 3D cam (only for anagliph pictures.
`
`75 mm Fujifilm W3 cam.
`
`77 mm Fujifilm W1 cam.
`
`88 mm Loreo 3D lens for digital cams.
`
`140mm Cyclopital3D base extender for the JVC TD1 and Sony TD10.
`
`200mm Cyclopital3D base extender for the Panasonic AG-3DA1.
`
`225mm Cyclopital3D base extender for the Fujifilm W1 and W3 cams.
`Base line selection
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`For general purpose stereo photography, where the goal is to duplicate natural human vision an