The stereoscopic 3D world is full of terms that cause confusion. The 3D Focus stereoscopic 3D glossary aims to simplify the jargon.

review dividing line 3D GLOSSARY


2D Plus Delta
An Open Standard used in the H.264 implementation of Multiview Video Coding that allows a full resolution 3D image to be encoded in a 2D image that remains readable to legacy 2D decoders and only adds between 30% and 60% to 2D bit-rates.

2D to 3D conversion
Allows the use of 2D images in a 3D production up to a certain level. Certain shots work well, others can actually have a negative effect.

3D Zoom control
One control that allows the cameraman to control zoom and focus on 2 cameras. Alignment process the process of aligning 2 cameras. This has 3 main areas when using the Element/Sony system.

  • Optical alignment that ensures both lenses zoom into themiddle of the camera chip block.
  • Mechanical alignment where the rig is adjusted mechanically so the 2 cameras are producing “identical” frames
  • Digital alignment where any issues that could not be corrected mechanically are resolved using the 3D box

Generally used in theme parks but in some countries present in mainstream cinemas 4D-Film uses stereoscopic 3D projection plus the addition of simulated real-world effects such as rain, wind, vibrations and in the case of Honey, I Shrunk the Audience, rats. Avatar and Kung Fu Panda 2 are among other films to be released in this format.

Active/shutter 3D glasses 
Glasses that actively block alternate eyes from seeing the screen in synchronization with images projected for each eye one after the other. Active shutter glasses use a layer of LCDs to block each eye and are kept in synchronization through an Infra Red signal transmitted from near the screen. Active shutter technology is relatively cheap to implement on LCD Televisions due the ability of the manufactuer to add a relatively cheap IR controller to screens that have fast enough refresh rates. One drawback in this approach is the high price of glasses when compared to passive displays while others also cite flickering in the viewer's peripheral vision as a potential problem.

Aerial perspective
This is the reduction in contrast and saturation of objects that a further away. It is important to add this effect when creating 3D CGI scenes and is sometimes referred to as distance fog.

Alignment Plate
The plate that has all the adjustment gearing for picture alignment. Roll, Pitch and Z axis.

An outdated way of seeing 3D on a 2D monitor, using the red/blue colouring that everyone remembers from Jaws 3D, etc. There have been improvements along the way (Colour‐code for example) but it is still tiring to watch for any length of time. In production it is still used as a way of seeing 3D and also occasionally by convergence pullers who look at the red/blue image in 2D and judge the stereo within the picture.

One of cinema's most well established camera and equipment makers, Arri have a long history in making film cameras and currently produce a number of Digital Cinema Cameras used for 3D production including the Arriflex D20 and D21 and the 2.9K high-dynamic-range capable Alexa.

Autostereoscopic display
Otherwise know as glasses free 3D, this display type varies from screens that must be viewed from a specific central position (such as on the Nintendo 3DS) to those which can be viewed from multiple angles such as those made by German manufacturer Tridelity.

Beam Splitter
The mirror in the large box at the front of the mirror rigs. The “mirror” is in fact a 50/50 beam splitter allowing 50% of the light through to one camera and reflecting 50% of the light to the other.

Blu-ray 3D
The system uses Sony's Blu-ray Discs in tandem with Multi View Video Encoding to allow films to be consumed in full HD in both Blu-ray 3D players and legacy 2D Blu-ray players.

The forces behind Avatar and a host of other 3D blockbusters and live events, this is the company that has lead the current 3D revolution. Titanic, Terminator 2, Aliens, Abys and Avatar director, James Cameron and his long time Stereographer, technologist and working parter Vince Pace combine to lead this innovative group .

The ability to display the images from two cameras as one display, based on a checker or chess board layout. This enables very accurate colour balance between the two cameras.

A method of adding a sense of depth to printed or screen-based images. Chromadepth makes red colours look closer than the page or screen and blues look further away. The system us a patented technique using defracting glasses and relies on  the differences in diffraction of the various frequencies of light.

This refers to where in 3D space the physical screen plane is. The point of convergence is where an object within a frame appears as one (both images sit perfectly on top of each other) it is at this point that the screen plane is and objects in front will appear to be out of the screen and objects behind will appear to be into the screen.

Convergence Operator Control
The movement of the rig during filming and dictate under the Stereographer’s guidance the amount of 3D in any given shot. Also called Convergence Puller.

Depth Budget
This is the amount of “stereo” or 3D that is set prior to filming for the 3D department to adhere to, typically it is talked of as a percentage.

Dense Point Cloud Mapping
The method of creating a virtual 3D model from a scene using RGB-D cameras, researched by teams at the University of Washington and MIT.

Difference Matte
Most Convergence Operators use a 2D screen displaying a difference matte to judge the amount of stereo in a frame. To do this one eye is displayed as a black frame one frame is displayed as a white one. When shown on top of each other there is a grey frame with differences displayed in black or white. One convergence puller described his job as “watching TV in letraset!”.

The unnatural outward rotation of the human eyes to view images with an interocular that is larger than that of the average human eye (2.5”). Results in wall-eye.

Dolby 3D 
The proprietary system for 3D cinema projection from Dolby, this passive glasses variant uses filters that block different specific frequencies of red green and blue light for each eye, allowing full colour 3D to be produced without polarization. Dolby 3D uses expensive filters in the glasses rendering them too expensive to be considered disposable. The system is not usable on print mediums and has not yet been developed for LCD screens. In the cinema a filter wheel rotates over a digital projector in synchronisation with left and right eye frames which are projected one after the other. Dolby 3D provides exceptionally bright and clear images.

Dual Stream Record
Because the cameras produce 2 HD streams recording them can prove difficult. The Sony 5800, SRW1 and R1000 decks allow for these 2 streams to be recorded at  the same tape on the same tape or media with obvious benefits to sync.

Dual Link
An abbreviation referring to dual simultaneous full frame HD left and right eye signals. This is carried by 2 video cables.

Erasmus Recording Binocular (ERB-2)
The European Space Agency's second generation all-in-one stereoscopic 3D camera for use in space. The camera uses a side-by-side configuration and has recently been used in the first ever live 3D video transmission from space, aboard the International Space Station.

Floating Window
A mask added to the edge of the frame in post production to that has the effect of changing the perceived placement of the screen in the 3D space. This can be used to change the feel of a scene by making things outside the actual screen place seem inside it or vice versa and is also useful for eliminating edge of screen violations.

Frame violation
Where an object breaks frame but causes an uncomfortable viewing experience. This can be either because the object is too close to the camera when compared to the rest of the frame or that it appears in one camera but not the other. These violations tend to happen on the camera that is not being monitored by the cameraman.

Horizontal shift
Difference between the 2 images. Good 3D relies upon perfectly aligned images from 2 cameras with slight and controlled horizontal differences.

Cinema projection technology pairing RealD and Sony to provide RealD passive polarisation 3D with 4K resolution projector that allows for the concurent projection of 2K resolution images for each eye removing the need to show left and right images one after the other.

California based Digital Cinema Camera company founded in 2007 and headed by Jim Jannard, the former owner and founder of Oakley. RED specialise in making high resolution s35mm cameras that record in a proprietary compressed-RAW file format. These factors make RED cameras well suited to 3D by allowing more room for spacial and exposure/colour disparity correction. Cameras include the 4.5K RED One (used in Pirates of the Caribbean: On Stranger Tides) and new high-frame-rate 5K RED Epic.

Also known as RGB plus depth this is image capture that acquires a standard 2D view along side a 3D model of the scene using a single colour camera and a range camera. The most widely known example of these is the Kinect for xBox 360, developed by Isreali tech company PrimeSense.

Long running motion picture equipment specialists that make the Genesis camera and hire-out 'Panavised' cameras from the likes of Arri, Sony and RED as well as providing many other forms of motion picture equipment for the movie industry.

Passive 3D glasses
Used for viewing 3D content they act as a filter to block each eye from seeing the image intended for the other eye. These can include polarising, anaglyph or any other combination of coloured filters.

Silicon Imaging
Maker of the SI 2K, a small-form-factor 2K resolution camera that outputs a RAW image stream. Used on a number of 3D films the SI 2K is prized for it's light-weight and often used on handheld mirror rigs.

Sony CineAlta
A brand of digital video cameras developed by Sony and Panavision specifically for movie production. Used extensively by CAMERON | PACE, CineAlta cameras such as the F35 were used in Avatar and TRON: Legacy and the new F65 sports an 8K imager with a super-wide RAW colour space.

The biological perception of depth through visually perceiving two slightly different images of the world in each eye. Relying on binocular vision, in humans the effect of stereopsis occurs towards the centre of our sight, extends to objects within roughly 150 meters of the viewer and only accounts for roughly 55% (on average) of our overall perception of depth.

Possibly the simplest form of depth perception occlusion is the technical term for an object blocking the view of an other by being in front of it.

Motion parallax
The creation of disparity though movement which results in the perception of depth. Because objects move across our vision at different rates depending on their distance we can perceive their depth through movement. This effect is especially strong when moving quickly.

Multiview Video Coding (MVC)
A compression scheme new to H.264/MPEG4 AVC as of 2009 that is designed to allow multiple camera angles to be efficiently contained in one video stream.

A method of toeing in cameras that does not cause Keystoning due to the angling of camera sensors to compensate for the Keystoning effect. This rig set-up is used for virtual rigs in computer rendered stereo 3D but is exceptionally rare for real-world rigs due to the complexity of accurately angling camera sensors.

Stereo pair
A pair of images that when viewed using a 3D display creates the illusion of depth. All stereoscopic 3D consists of a stereo pair in some form or another.

Virtual rig
A pair of virtual cameras used to capture a 3D CGI model within a 3D animation or compositing programme such as Maya or Autodesk Flame.

Stereoscopic video coding
The general term for creating a stereo pair of images for transmission or storage. Methods include side-by-side compression within a standard HD stream, Anaglyph and Multiview Video Coding.

Witness camera
A camera used on set to provide depth information with which post production teams can use to guide them as they create a 3D representation of a scene that was originally captured in 2D.

Range Camera
A capture device that detects the distance of objects in a scene, creating the basis for a virtual 3D model of that scene. These can use technologies such as Time of Flight (a class of LIDAR that uses light from the non-visible spectrum), Stereo Triangulation, Structured Light and Interferometry.

Mirror Rig
A rig configuration using 2 cameras, where one camera is positioned vertically above or below the second camera. This configuration requires the use of a beam splitter to pass light to the vertical camera.

The rig in its broadcast mirror configuration where the top camera is a full body Sony HDC-1500 and the bottom camera is an HDC-1500 utilisingT‐Block head adaptor, which remotes the CCD block from the main camera body.

Small bodied HD Camera designed for beauty cam and 3D applications. Known as HDC-P1 they can be used in place of HDC-1500 full bodied cameras. Although small this camera uses the same CCD as the HDC-1500R allowing cameras to be mixed.

Inter Ocular/Inter Axial
Commonly termed IO this refers to the physical distance between the centre of 2 frames, or loosely how far the cameras are apart. NB: it is the relationship between the Convergence and Inter Axial that determines the amount of 3D.

An effect caused by the act of convergence where one image when laid over the top of the other has slight differences in the corners of the frame. This is because the frame no longer sits “flat” but is slightly angled in comparison to the other.

Lens Tapping/Matching
A pre alignment procedure that matches 2 lenses as closely as possible.

Where one camera is not sitting completely square to the other and the images viewed from one camera on top of the other appear to be higher one side of the frame, then correct in the centre and then lower on the other side of the frame.

The lead person of the 3D crew. He/she oversees all the 3D alignment before the shooting begins and then during filming oversees the quality of the 3D output feeding comments to his crew.

Stereo Engineer
Looks at all the data being fed back from the various 3D boxes and “tweaks” within the 3D Box any issues that arise during filming.

Vertical/Y shift
A misalignment of the 2 frames vertically, where a horizontal line in frame (e.g. the roof of a stand) appears higher in one camera than another on the same rig. This is serious and is a major cause of viewing discomfort.

Z axis
The axis from front to back of a 3D image, i.e. into and out of the screen.

Separation on the screen plane between left and right images of an object. Determines the perceived depth of objects relative to the screen plane.

Negative Parallax
Ojects are perceived to be positioned within the viewer’s space (or “personal space”), i.e. in front of the screen plane.

Positive Parallax
Objects are perceived to be positioned within the screen space (or “world space”), i.e. beyond the screen plane.

Zero Parallax
Objects are positioned at the screen plane, and appear to be in two dimensions.

Screen Plane
The plane of the display  or the surface of the movie screen, TV screen, or computer screen.

(or “toeing-in”), inward rotation of the lenses, to shift the parallax of the scene and the perceived depth of objects relative to the screen space.

Point of Convergence
The position on the set where the axes of the lenses exactly overlap, defining the position of the zero parallax plane or screen plane.

(or “interaxial”), horizontal displacement of the lenses of the cameras.

The effect of an interocular that is larger than that of the average human eye (2.5”).

An artifact that results from use of wide-angle lenses or a larger interocular than that of the average human eye (hyperstereo).

The effect of an interocular that is smaller than that of the average human eye (2.5”).

An artifact that results from use of a smaller interocular than that of the average human eye (hypostereo).

The effect of shooting with parallel lenses and an interocular that approximates that of the average human eye.

An artifact that results from the use of long focal length lenses.

(or “trapezoidal distortion”), an artifact that results from excessive convergence of the lenses.

An uncomfortable condition that results from the attempt to fuse objects with strong positive parallax and a wider-than-normal interocular.

Side by Side Compression
A method of utilizing horizontal compression on the individual the left and right eye HD video frames to reduce their size, so that once combined left and right eye frames can be transmitted within a single HD video frame. This compression method enables 3D signals to be synchronously delivered using standard HD distribution equipment.

Side by Side Rig
A rig configuration using 2 cameras filming side by side.

RealD Cinema - is a digital stereoscopic projection technology made and sold by RealD Inc. It is currently the most widely used technology for watching 3-D films in theatres and is based on circularly polarized light. Glasses used for viewing are simple filter based units, known as “passive” glasses. These same glasses can be used with Sony professional displays as these are also RealD compatible.