glossary

A

Academy aperture: A specific 35mm film framing.

Accomodation: The focusing of the eyes – or more properly, the ability of the eyes lenses to change shape in order to focus.

Active region: The portion of the video signal that is used for actual image information, as opposed to blanking, closed-captioning, time code, etc.

Affine: Any linear geometric transformation including pan, rotate, scale, and shear.

AIFF: Audio Interchange File Format. A standard file format for storing audio data.

Algorithm: A procedure or set of instructions for solving a problem or accomplishing a particular goal.

Aliasing: An artifact that is due to limited resolution.

Alpha channel: The portion of a four-channel image that is used to store transparency information.

Ambient light: in CG, a directionless light source that uniformly distributes light in all directions, illuminating object equally regardless of their surface orientation.

Ambient occlusion: CG shading method that uses a type of global illumination to better compute self-shadowing of objects. Often used in compositing as part of a multiple-pass rendering workflow.

Analog: Information/ data that is continuously variable, without discrete steps or quantization. As opposed to digital.

Anaglyph: Wavelength selection using complimentary colored images and color filets to filter or pass the appropriate perspective views to the appropriate eyes.

Anamorphic: Any distorted image that can be undistorted to restore it to its original format.

Anamorphic format: A film format characterized by the fact that the image captured on the negative is horizontally squeezed by the use of a special lens. It is later unsqueezed at projection time by the appropriate amount. For most 35mm feature-film work, the standard anamorphic format produces a 2.35:1 aspect ratio when projected. See Cinemascope, Panavision.

Anamorphic lens: A lens that changes the width-to-height relationship of the original image. The most common anamorphic camera lenses in film work compress the horizontal axis by 50%. See Cinemascope.

Animated: Having characteristics that change over time.

Animatic: A rough animation that gives some idea about the timing of a sequence. Essentially a moving storyboard.

Animation: Moving imagery that is created on a frame-by-frame basis. This may be accomplished via the use of computers or with more traditional eel animation techniques.

Animation rig: CG structure built for the CG model and used by an animator as a type of skeleton to pose the animation model.

Animator: A person responsible for producing animations.

Anisotropic: Having properties (such as color or reflectivity) that differ based on the direction of measurement.

Answer Print: The first print from the lab containing synchronized image and sound and which has had all of the scenes color balanced.

Antialiasing: Techniques used to mitigate the artifacts caused by a lack of sufficient resolution.

Aperture: (1) In a lens, the size of the opening that light passes through (usually given in terms of its £-stop or t-stop). (2) In a camera body, the mask opening that defines the area of film that will be exposed on each frame. (3) In a projector, the mask opening that defines the area of the frame that will be projected.

API: Abbreviation for Application Programming Interface. 

Articulate matte: A matte whose shape changes over time and which is designed to accurately follow the contours of the object to which it corresponds.

Artifact: A (usually undesirable) item in an image that is a side effect of the process used to generate or modify that image.

ASA rating: A standard numerical rating for specifying a film’s sensitivity to light. “ASA” refers to the American Standards Association, now known as the American National Standards Institute, or ANSI. Many manufacturers now use their own specific exposure index instead. See also DIN rating, ISO index.

ASCII: Abbreviation for American Standard for Computer Information Interchange. A very common alphanumeric text interchange format. The term is used colloquially to refer to data that is stored in a text format that doesn’t require a special program to decode and is usually somewhat comprehensible to a human reader.

Aspect ratio: A single number that is the result of dividing the width of an image by its height. The units used to measure the width and height are irrelevant, since they will cancel when divided together to give a unitless result. See also pixel aspect ratio.

Atmosphere: A depth cue that causes objects to decrease in contrast as they move into the distance.

B

Background: In a composite, the bottom element over which all others are added. In general, the background makes up the majority of the image.

Backing color: The color of the uniform background that is used when shooting an element for traveling matte extraction.

Bake in: Term used to mean that whatever settings, composite layers, color, animation, and so on have been used, have been permanently set in the shot.

Baked out: To output in a format that is fixed (for example 3D animation baked out to a series of meshes, one per frame)

Banding: An artifact that appears in areas of a color gradient where the lack of sufficient color resolution causes noticeable bands instead of a smooth transition. Also known as contouring. See also Mach banding.

Base: The transparent material (usually cellulose acetate) on which emulsions are applied to make photographic film. Note that it is generally not completely transparent, but rather has a slight characteristic color that may need to be compensated for when scanning.

Batch compositing: A method of compositing that entails the creation of a script or set of instructions that will be executed at a later time.

Beauty pass: When using motion control to shoot multiple passes of an object, the beauty pass is the one that features the most significant information about the object, in contrast to other passes such as the lighting pass, shadow pass, or reflection pass.

BG: Abbreviation for background.

Bézier curve: a urved line or path defined by mathematical equations. It was named after Pierre Bézier, a French mathematician and engineer who developed this method of computer drawing in the late 1960s while working for the car manufacturer Renault.

Bicubic interpolation: A method of interpolation based on an average of the 16 nearest neighbors. See also linear interpolation, bilinear interpolation.

Bilinear interpolation: A method of interpolation based on an average of the four nearest neighbors. See also linear interpolation, bicubic interpolation.

Bit: The basic unit for representing data in a digital environment. A bit can have only two different values: 0 or 1.

Bit depth: A way of specifying the color resolution in an image by measuring the number of bits devoted to each component of the pixels in the image.

Bit-mapped image: An image that consists of a rectangular, two-dimensional array of pixels. The standard method for representing an image in a digital format.

Black point: (1) On a piece of film, the measured density in the area of greatest opacity. (2) In a digital image, the numerical value that corresponds to the darkest area that will be represented when the image is eventually viewed in its final form.

Bleach bypass: term used to describe a number of film processing techniques offered by various labs, in which the bleaching function done during normal processing is partially or completely skipped as a means of increasing contrast and reducing saturation. Also called ENR.

Bluescreen: (1) Commonly used as a generic term that refers to bluescreen photography or any similar process, which may use other colors as well as blue. (2) Literally, a screen of some sort of blue material that is suspended behind an object for which we wish to extract a matte. Ideally, the bluescreen appears to the camera as a completely uniform blue field.

Bluescreen photography: The process of photographing an object in front of a bluescreen with the intention of extracting a matte for that object using various keying and/ or color-difference techniques.

Blue spill: Any contamination of the foreground subject by light reflected from the bluescreen in front of which it is placed. See also spill, green spill.

Bokeh: is the blur, or the aesthetic quality of the blur, in out-of-focus areas of an image, or “the way the lens renders out-of-focus points of light.” It’s the appearance of point-of-light sources in an out-of-focus area of an image produced by a lens with a shallow depth of field.

Bounce light: Light that is reflected or “bounced” off other objects in a scene before it reaches the subject.

Bounding Box: The smallest regular-shaped box that encloses a 3D object, usually rectangular in shape

Box filter: A specific digital filter that is often used when resampling a digital image. The Box filter is fast, but fairly low quality.

Bump Map: A black-and-white image used by a 3D software package to simulate the three-dimensional detail on the surface of an object. When projected over the surface of the object, parts of the surface beneath white areas of the image are raised; those beneath black areas are depressed. Bump mapping is purely a rendering effect, however, and does not affect the underlying geometry of the model.

Burn-in: Photographic double exposure of an element over a previously exposed piece of film.

B-Spline: a generalization of a Bezier curve.

C

Camera aperture: A specific 35mm film framing, also known as full aperture.

Camera frustrum: what the camera sees.

Camera mapping: a technique in which an image is projected from the camera onto a 3D object. This technique is useful for re-creating a simulation of a 3D environment using 2D photographic elements. Also called projection mapping.

Caustics:  Patches of intense illumination caused by the refraction of light through a transparent object or the reflection of light from a reflective surface. One common example would be the shifting patterns of light and shade cast on the floor of a swimming pool on a sunny day.

CCD: Abbreviation for charge-coupled device, a light-sensitive semiconductor that is often used in scanners and video cameras to capture an image.

Cel animation: Animation that is the result of sequences of images drawn on individual clear acetate eels. Many aspects of traditional eel animation are now being supplemented by digital techniques.

Center extraction: A term used to describe any process, such as masking or cropping, that is used to extract the centered portion of the original image to produce the final viewing format.

Centroid: The geometric center of an object.

CGI: See computer-generated imagery.

Channel: For a given image, the subimage that is composed only of the values from a single component of each pixel.

Characteristic curve: A curve that plots the relationship between light falling on a piece of film and the resulting density of the developed image.

Chroma-keying: A keying technique that allows one to separate an object from its background based on colors that are unique to either the foreground or background.

Chromatic aberration: An image artifact that is caused by the fact that different wavelengths of light are bent by slightly different amount as they pass through a lens. The artifact is usually seen as a color shift along sharply delineated edges in an image.

Chromatic resolution: Another term for color resolution.

Chrominance: The color portion of a video signal, carrying the hue and saturation values. See also luminance.

Cinemascope: An anamorphic film format that produces an image with an aspect ratio of 2.35:1. Although Cinemascope (or CinemaScope) was originally a specific process developed by 20th Century Fox in the 1950s, it has become a generic term for the 2.35 anamorphic format. The most common lenses used for this purpose today are produced by Panavision.

Cineon: A specific image file format for film.

Circle of confusion: The size of the circle to which an idealized point will diverge when the lens is focused at different depths. Used as a way to measure the focus of a lens.

Clean plate: A plate that differs from the primary plate only in that it does not contain the subject(s) in the frame.

Clip: A small piece of film, often “clipped” from a longer shot, that can be used as a reference for color, lighting, etc.

Clipping: The process (intentional or otherwise) whereby data above or below a certain threshold is removed or lost. With digital images, this usually translates to colors outside a specific range.

Cloud tank: A large water-filled glass enclosure that is used to create clouds and other atmospheric effects. The clouds are usually produced by injecting some opaque liquid (such as white paint) into the water.

CLUT: Abbreviation for Color Look-Up Table 

CMY: Cyan, magenta, and yellow. The three complementary colors, or a method of specifying the colors in an image based on a mix of these three components.

Codec: Abbreviation for Compression/Decompression.

Color correction: Any process that alters the perceived color balance of an image.

Color difference method: A compositing technique that utilizes the difference in color between the different channels of an image in order to extract a matte. The technique relies on the subject being photographed in front of a uniformly colored background, such as a bluescreen.

Color resolution: The amount of data allocated for specifying the value of an individual color in an image. See also bit depth.

Color space: Any method for representing the color in an image. Usually based on certain components such as RGB, HSV, etc.

Color temperature: A method of specifying color based on an absolute temperature scale, degrees Kelvin (K). The color is equivalent to the color of light that would be emitted if a pure black object were heated to that temperature. Higher color temperatures are more blue, lower temperatures are more red.

Color timer: A person who adjusts the scene-to-scene color continuity when preparing the final print of a film.

Color timing: The color balance of a particular image or scene, or the process of color correcting and balancing that image or scene.

Color wedge: A series of images that feature incremental alterations in the color of a certain element (or sometimes the entire frame) for the purpose of choosing a final value for the color of that element.

Complementary color: The color that results when the primary color is subtracted from white.

Complementary matte: The matte that results when the primary matte is inverted.

Component: One of the elements that is used to define the color of a pixel. In most digital images, the pixel color is specified in terms of its red, green, and blue components.

Component video: Video signal in which the luminance and chrominance elements are maintained separately.

Composite video: Video signal in which the luminance and chrominance elements are combined (encoded) into a single signal.

Compositing: The manipulated combination of at least two source images to produce an integrated result.

Compositing engine: Within a package used for compositing, the code that is responsible for the actual image processing operations, in contrast to other code that may deal with the user interface, file input/ output, etc.

Compositor: A person who creates composites.

Compression ratio: The ratio of the data sizes between the uncompressed element and the compressed equivalent.

Computer-generated imagery: An image or images created or manipulated with the aid of a computer. Often used to refer specifically to 3D computer animation although it is really a much broader term.

Computer graphics: An image or images created or manipulated with the aid of a computer.

Constrain: To restrict the motion of an object to one or two planes, or to a certain range of values within a plane, in order to simplify the process of animation. Constraints are commonly imposed on joints within a skeleton during the process of rigging a  character for animation, in order to prevent that character from performing actions that would be physically impossible.

Continuity: The smooth flow of action or events from one shot or scene to the next, without any indication that the different shots/scenes may have been photographed at different times or processed differently.

Contouring: An artifact that results from not having enough color resolution to properly represent a color gradient. See also Mach banding.

Contrast: The ratio of the brightest tones in an image to the darkest.

Control points: The specific points that are interpreted to define the shape of a curve.

Convolution filter: A matrix of numbers used to control the weighted averaging performed in a convolve operation. Sometimes also referred to as the convolution mask.

Convolution kernel: The group of pixels that will be considered when performing a convolve operation. Generally we are only worried about the size of the kernel, which is usually a square matrix with an odd number of elements in each dimension. The most common kernel size is 3 X 3. Occasionally the term is used as a synonym for the convolution filter.

Convolution mask: See convolution filter.

Convolve: An image processing operation that involves the specialized averaging of a neighborhood of pixels using a convolution filter. Also known as a spatial convolution.

Cool: A nonexact term that is used to describe an image that is biased toward the blue portion of the spectrum.

CPU: Abbreviation for central processing unit, the computational heart of a computer

Crawling: An undesirable artifact characterized by edges that do not remain stable over time.

Cropping: The removal (intentionally or otherwise) of part of an image that is outside a specific boundary.

C-scope: Abbreviation for Cinemascope.

Cukaloris: Panel with irregular holes cut in it to project patterned shadows onto a subject. Also known as a kukaloris, cuke, or cookie.

Cursor: A graphical marker, usually controlled by a device such as a mouse or a tablet, that is used to point to a position or object on a computer’s display.

CV:  Control Vertex. A control point used to manipulate the shape of a NURBS curve/surface.

D

D1 format: A digital component video format. 01 is considered to be a nearly lossless format.

D2 format: A digital composite video format. 02 is a lower quality than Dl, but is also significantly less expensive.

D5 format: A digital component video format. 05 is considered to be of the same quality as Dl, and also has provisions for storing HDTV-format imagery.

Dailies: Imagery produced during the previous day’s work, or a meeting to view this work.

Decibel (dB): Unit of loudness measured on a logarithmic scale. The human ear can perceive a 1 dB change in loudness.

Decimation: The process of throwing away unnecessary information when reducing the size of an image.

Decoder: A device that separates a composite video signal into a component video signal.

Deinterlace: The process of separating the two fields that make up a video image into two distinct images.

Densitometer: Instrument used to measure the optical density of a piece of processed film.

Density space: A nonlinear color space that is based on the density of a piece of developed negative relative to the amount of light that reached it.

Depth channel: Another term for the Z-channel.

Depth cue: Information that helps to determine the distance of an object from the camera.

Depth of field: The depth of field of a specific lens is the range of acceptable focus in front of and behind the primary focus setting. It is a function not only of the specific lens used but also of the distance from the lens to the primary focal plane, and of the chosen aperture. Larger apertures will narrow the depth of field; smaller apertures will increase it.

Depth of focus: A term that is often improperly used when one wishes to refer to the depth of field. Depth of focus is a specific term for the point behind the lens (inside the camera body) where a piece of film should be placed so that the image will be properly focused. desaturation: A term to describe the removal or loss of color in an image. A completely desaturated image would consist only of shades of gray.

Detail generator: An adjustment available on some video cameras that introduces additional sharpening into the captured image.

Difference matte: A matte created by subtracting an image in which the subject is present from an otherwise identical image in which it is not present.

Diffusion: An effect, caused by atmosphere or special filters placed on the lens, that is characterized by a scattering of light, elevated dark areas, and an overall softer look.

Digital: A method of representing data via discrete, well-defined samples. As opposed to analog.

Digital compositing: The digitally manipulated combination of at least two source images to produce an integrated result.

Digitization: The process of sampling any analog subject to produce a digital representation. Within the field of digital compositing, usually refers to theprocess of converting a video or film source to digital information.

Dilation: An image processing technique that results in brighter areas of the image increasing in size and darker areas decreasing. See also erosion.

DIN rating: A standard numerical rating for specifying a film’s sensitivity to light. “DIN” is an abbreviation for Deutsche Industrie Norm (German Industry Standard). Many manufacturers now use their own specific exposure index instead. See also ASA rating, ISO index.

Dirac filter: Another name for the impulse filter.

Director: The person with the primary responsibility for overseeing the creative aspects of a project or production.

Displacement map: A recent advance on Bump Mapping. Like a Bump Map, a Displacement Map is a black-and-white image that a 3D software package projects over the surface of a model to generate surface detail. Unlike a bump map, however, a Displacement Map modifies the actual underlying geometry and is not merely a rendering effect.

Dissolve: A specific transition effect in which one scene gradually fades out at the same time that a second scene fades in. Halfway through a linear dissolve the image will be a 50’/r. mix of both scenes.

Dither: A method for representing more colors than would normally be available with a given palette. Dithering uses combinations of colored pixels and relies on the fact that the human eye will average them together and interpret the result as a new intermediate color.

D-max: See maximum density.

D-min: See minimum density.

DOD: Abbreviation for domain of definition.

DOF: Abbreviation for depth of field.

Domain of definition: A (usually rectangular) region that defines the maximum boundaries of useful information in an image. Generally, everything outside of the DOD will have a value of 0 in all channels of the image. The DOD is usually determined automatically, as opposed to a region of interest.

Dots per inch: A common method for measuring spatial resolution in the print industry. The horizontal and vertical scales are assumed to be equal, unless specified otherwise.

Double exposure: In the optical world, a double exposure is accomplished by exposing two different images onto a single negative. The result is a mixture of the two images. In the digital world, this effect is accomplished by mathematically averaging the two images.

Double framing: The process of duplicating and repeating every frame in an image sequence. The result is a new image sequence that appee1rs to be moving at half the original speed. Also known as double printing.

DPI: Abbreviation for dots per inch.

Drop frame: Video footage in which two frames me dropped every minute except the tenth. It is used to compensate for the fact that time code works at exactly 30 frames per second but NTSC video runs at only 29.97 fps.

Dubbing: The process of making <1 copy of a video tape.

Dust busting: The term used to describe the process of removing dirt and scratches from scanned imagery.

DVE: An abbreviation for digital video effect, this usually refers to any of a number of geometric transformations that are typically performed by specialized real-time video equipment. Examples of a DVE move include anime1ted pans, rotations, or flips, as well as various hardware-specific effects such as page turns or customized wipes.

DX: Abbreviation for double exposure.

Dynamic range: (1) The range of brightness values in a scene or an image, from brightest to darkest, often expressed as a ratio. (2) In a digital image, the total number of different colors in the image.

Dynamic resolution: Another term for color resolution.

E

Edge detection: An algorithm used to enhance or isolate transition areas, or “edges,” in an image.

Edge matte: A specialized matte that includes only the outlines or borders of an object.

Edge numbers: Sequential numbers printed along the edge of a piece of film by the manufacturer to help identify particular frames.

Editing: The process of assembling shots and scenes into a final product, making decisions about their length and ordering.

Effects animation: A term that is usually used to refer to elements that were created via eel animation or digital rotoscoping techniques but are not character related. Common examples include sparks, lightning, or smoke.

Effects filter: Any of a number of different optical filters that can introduce diffusion, flares, glows, etc. Dangerous when shooting bluescreen elements.

EI: Abbreviation for exposure index.

8-bit image: any image containing 8-bit of color information per channel.

Eight-perf: A nickname for the Vista Vision film format that comes from the fact that each Vista Vision frame has eight perforations along each edge.

Element: A discrete image or sequence of images that will be added to a composite.

Emulsion: The light-sensitive material that is applied to a transparent base to create photographic film.

Encoder: (1) A piece of video equipment that combines a component video signal into a composite video signal. (2) A generalized term used to refer to a number of different data capture devices, usually ones that convert measurements into digital data.

Environment map: An image intended to entirely enclose a scene, either to provide a convincing background, or to project real-world lighting or reflection data onto the surface of an object.

Erosion: An image processing technique that results in darker areas of the image increasing in size and brighter areas decreasing. See also dilation.

E-split: See exposure split.

Exposure index: A standardized, but manufacturer-specific, numerical rating system for specifying a film’s sensitivity to light. There are also several industrystandard systems in use, including the ASA rating, the ISO index, and the DIN rating. To make it even more interesting, many manufacturers will specify a rating for both daylight lighting and tungsten lighting.

Exposure latitude: Amount of over- or underexposure a given type of film can tolerate and still produce acceptable results.

Exposure sheets: Sheets that tell the Oxberry camera, or downshooter, cameraman in what order to layer and shoot the animation cels and for how many frames per cel, per layer. Also called x-sheets.

Exposure split: A simple split-screen shot in which multiple exposures of a given scene are combined in order to bring areas of widely divergent brightness into the same shot. Also known as an E-split.

Exposure wedge: A series of images that feature incremental alterations in the exposure (brightness) of a certain element (or sometimes the entire frame) for the purpose of choosing a final value for the exposure of that element.

Expression: A mathematical formula used to define the value of a given attribute of an object during animation. The use of expressions forms a procedural alternative to hand, or keyframe, animation.

Extrusion: A modelling technique in which a two-dimensional outline or profile is duplicated outwards along a linear path, and the set of duplicated profiles joined to create a continuous three-dimensional surface.

F

Fade: Decreasing the brightness of an image over time, eventually resulting in a black image.

Fall-off: The way in which the intensity of a light diminishes with the distance from its source. In the real world, the fall-off of light is governed by the inverse square law, which states that the intensity is inversely proportional to the square of the distance. However, in 3D software packages, it is possible to use a variety of different mathematical formulae to describe the relationship.

Fast Fourier transform: An algorithm for converting an image so that it is represented in terms of the magnitude and phase of the various frequencies that make up the image. Yes, there is a regular Fourier transform, but nobody uses it because it’s not … fast.

FFT: Abbreviation for fast Fourier transform.

FG: Abbreviation for foreground.

Field: (1) An image composed of either the even or odd scan lines of a video image. Two fields played sequentially will make up a video frame. (2) A unit of measure on a field chart.

Field chart: A method of dividing an image into a grid so that certain areas of the frame can be specified by grid coordinates.

Field dominance: The order in which the fields in an interlaced image are displayed. Essentially, whether the even or the odd field is displayed first for any given frame.

Field of view: The range of a scene that will be captured by a specific camera. FOV is usually measured as the number of horizontal degrees (out of 360), although a vertical field of view is also a valid measurement.

File format: A standardized description of how a piece of data (such as an image) is to be stored.

Film gauge: The width of a particular film stock, i.e., 16mm, 35mm, etc.

Film recorder: A device that is capable of transferring digital images to a piece of film negative.

Film recording: The process of transferring digital images to a piece of film negative via the use of a film recorder.

Film speed: A very context-dependent term that may refer to (1) the rate that film is moving through a camera or a projector (24 frames per second in normal feature-film work) or to (2) the light sensitivity of the film itself. Slow-speed film is less light sensitive; high-speed film is more sensitive.

Film weave: Irregular horizontal movement (generally undesirable) of a piece of film as it moves through a camera or projector.

Filter: (1) A translucent material that is placed in front of a light or camera to modify the color that is transmitted. Certain of these optical filters may also be designed to introduce specific artifacts, such as diffusion, flares, etc. (2) Any of a number of algorithms used within the computer for sampling an image. Different filters can be used when transforming an image, and can result in differing amounts of sharpness or artifacts. (3) The process of using either of the aforementioned types of filters.

Final: The term given to a composite shot once it is considered complete and has been approved by the appropriate decision makers.

Fix-it-in-post: A phrase commonly used when time and/or conditions prohibit the ability to shoot a scene exactly as intended. Rather than delaying the production, a decision is made to shoot as quickly as possible and correct any problems during post-production.

Fixed matte: As opposed to a traveling matte, a fixed matte will not change position or shape during the shot.

Flare: Any of a number of effects that will show up on an image as the result of a light source shining directly into the lens of a camera.

Flashing: Flashing is an optical process whereby unprocessed negative is exposed to a small amount of light for the purpose of reducing the contrast or saturation of the scene that will eventually be photographed with that film. In the digital realm, flashing is the application of any number of nonspecific techniques to produce similar results. An image that appears to suffer from some of these characteristics is often referred to as appearing “flashed.”

Flat: Another term for low contrast.

Flat lens: Another term for a spherical lens. Sometimes also used as a relative term for measuring the distortion and exposure variance of any lens.

Flicker glasses: A type of 3D glasses that use an electronic shutter to block the light reaching each eye independently. By syncing the glasses to the projection device, alternate stereo pairs can be presented to the viewer in a fashion that simulates a stereoscopic scene.

Flip: A simple geometric transform in which an image is mirrored about the X-axis so that it is now upside-down. This process is different from merely rotating the image 180 degrees.

Float: A number defined with floating point precision

Floating point: A term used to describe a number in which no fixed number of digits must be used before or after a decimal point to describe a number, meaning that the decimal point can float.

Flop: A simple geometric transform in which an image is mirrored about the Y-axis.

Focal length: A measure of the magnification power of a given lens, based on the distance from the center of the lens to the film. Also known as simply the “length” of a lens. A longer focal length will produce greater magnification than a shorter length.

Focus: (1) To adjust a lens so that the image it produces is as sharp as possible. (2) The point in space behind a lens where this sharpness occurs.

Folding: The process of consolidating discrete mathematical operations into a single function.

Forced perspective: A technique used to create the illusion of increased depth in a scene by building more distant objects at a smaller scale than normal.

Foreground: Usually the primary element to be added to a composite and placed over the background. Often, there may be several foreground elements in a composite.

Format: (1) The size, resolution, aspect ratio, etc. for a given image. (2) The file format for a given image. (3) The physical medium (such as film, video, etc.) used to capture or display an image sequence. (4) A multitude of additional variations and subcategories of the first three definitions.

Forward Kinematics: Often abbreviated to FK, Forward Kinematics is a character animation technique for controlling the motion of the bones in a chain – for example, a limb – in which rotations propagate from bone to bone towards the free end of the chain (in the case of a limb, towards the hand or foot).

Four-perf: A nickname for the standard 35mm film format that refers to the fact that each frame spans four pairs of perforations.

Four-point track: A type of 2D tracking in which four points are selected from a sequence of images to extract an approximation of an object’s movement relative to the camera. It allows for corner-pining techniques.

4:1:1 / 4:2:2 / 4:4:4 compression: A method of encoding image data by sampling Y (luminance) and UV (chrominance) at different rates.

FOV: Abbreviation for field of view.

Fps: Abbreviation for frames per second. See frame rate.

Fractal compression: A lossy image-compression algorithm that is based on repeated use of scaled and rotated pixel patterns.

Frame: A single image that is usually part of a group designed to be viewed as a moving sequence.

Frame rate: The rate at which sequences of images are captured or displayed. The frame rate is usually measured in frames per second, or fps.

Freeze: The process of stopping the action. In digital compositing, this is usually accomplished by repeating the same frame for a duration of time.

Freeze frame: A single frame that is held for a duration of time.

Fringing: An artifact of the matting process in which a foreground element has a noticeable (usually bright) outline.

Frustrum: Term (CG) used to describe the 3D region that is visible on the screen (formed by a clipped pyramid).

Frustrum culling: The process of removing objects that lie completely outside the viewing frustrum from the rendering process.

F-stop: A measurement of the aperture of a lens.

Full aperture: A specific 35mm film framing, also known as camera aperture.

G

Gamma: (1) In film, a measure of the contrast of an image or emulsion, based on the slope of the straight-line portion of the characteristic curve. (2) An adjustment applied to a video monitor to compensate for its nonlinear response to a signal. (3) A digital effect used to modify the apparent brightness of an image.

Gamut: The range of colors that any given device or format is able to display or represent.

Garbage matte: A rough, simple matte that isolates unwanted elements from the primary element in an image.

Gauge: See film gauge.

Gaussian blur: A specific method for blurring an image based on a Gaussian filter.

Gaussian filter: A specific digital filter that is often used when resampling an image.

Gel: Abbreviation for gelatin filter, a flexible colored optical filter.

Generation loss: The loss of quality of an image due to repeated duplication. Generation loss is significantly reduced and in some cases completely eliminated when dealing with digital images.

Geometric transformation: An effect that causes some or all of the pixels in a given image to change their current location. Such effects include translation, rotation, scaling, warping, and various specialized distortion effects.

GIF: Graphics Interchange Format, a specific image file format.

Global illumination: A general term used to describe the modeling of all the reflected and transmitted light that originates from every surface in a scene.

Glue code: Code that ties different parts of the pipeline together, whether it’s data interchange between programs that write different file formats or interprocess control of one piece of the pipeline by another.

G-matte: Abbreviation for garbage matte.

Gobo: see cukaloris.

Grading: Another term for color timing, used primarily in Great Britain.

Grain: The individual particles of silver halide in a piece of film that capture an image when exposed to light. Because the distribution and sensitivity of these particles are not uniform, they are perceived (particularly when projected) as causing a noticeable graininess. Different film stocks will have different visual grain characteristics.

Graphical user interface: A user interface that utilizes images and other graphical elements to simplify the process of interacting with the software. Also known as the “look and feel” of the software.

Gray card: A card (gray) usually designed to reflect about 18% of the light that strikes it; used as a reference for measuring exposure.

Grayscale image: A completely desaturated image, with no color, only shades of gray.

Greenscreen: Identical in use and concept to a bluescreen (only it’s green).

Green spill: Any contamination of the foreground subject by light reflected from the greenscreen in front of which it is placed. See also spill, blue spill.

GUI: Abbreviation for graphical user interface.

H

Halation: A blurring or spreading of light around bright areas on a photographic image. Also seen as a glow on a monitor or TV screen. Most films have an anti-halation backing to keep the light from bouncing around in the camera and adding unwanted exposure (or halation)

Handles: Extra frames at the beginning and end of a shot that are not intended for use in the final shot but are included in the composite in case the shot’s length changes slightly.

HDRI: Abbreviation for high dynamic range imaging.

HDTV: High-definition television. A proposed new television standard with significantly greater spatial resolution than standard NTSC, PAL, or SECAM.

Hermite curve: A specific type of spline curve that allows for explicit control over the curve’s tangent at every control point.

High dynamic range: Related to imagery or devices that can deal with a larger than normal dynamic range.

High-pass filter: A spatial filter that enhances high-frequency detail. It is used as a method for sharpening an image.

Histogram: A graphical representation of the distribution (usually frequency of occurrence) of a particular characteristic of the pixels in an image.

Histogram equalization: An image processing technique that adjusts the contrast in an image so that it fits into a certain range.

Histogram sliding: Equivalent to adding a certain number to the values of every pixel in an image.

Histogram stretching: Equivalent to multiplying the values of every pixel in an image by a certain amount.

HLS: Hue, luminance, and saturation. A method of specifying the colors in animage based on a mix of these three components.

Hold: To stop the action by using the same frame repeatedly.

Hold-out matte: A matte used to prevent a foreground element from completely obscuring an object in the background plate.

Hot: A nonexact term for describing an image that is too bright. Completely unrelated to the terms warm and cool.

HSB: Hue, saturation, and brightness. A method of specifying the colors in an image based on a mix of these three components.

HSI: Hue, saturation, intensity. A method of specifying the colors in an image based on a mix of these three components.

HSL: Hue, saturation, and lightness. A method of specifying the colors in an image based on a mix of these three components.

HSV: hue, saturation, and value. A method of specifying the colors in an image based on a mix of these three components.

Hue: A specific color from the color spectrum, disregarding its saturation or value.

Huffman coding: A lossless image-compression scheme. See also run-length encoding, JPEG, MPEG.

I

ICC: Abbreviation for International Color Consortium

Image processing: The use of various tools and algorithms to modify digital images within a computer.

Image-based lighting (IBL): A technique in which a photographic reference image is used as an environment map to control the surface illumination of a 3D object, in order to create subtle real world lighting effects.

IMAX: A proprietary film capture/projection process that uses an extremely large-format negative.

Impulse filter: A specific digital filter that is often used when resampling a digital image. It is considered to be the lowest-quality, highest-speed filter in common use. Also known as the Dirac filter or the nearest-neighbor filter.

In-betweening: The process of interpolating between the keyframes of an animation sequence.

In-camera effects: Visual effects that are accomplished solely during principle photography, involving no additional postproduction.

Indexed color: A method of storing image data, in which the value of the pixel refers to an entry in a table of available colors instead of a numerical specification of the color itself.

Interframe coding: The process used in MPEG encoding whereby intermediate images in a sequence are defined by their deviation from specific keyframes.

Interlacing: The technique used to produce video images whereby two alternating field images are displayed in rapid sequence so that they appear to produce a complete frame.

Intermediate: General term used for copies (not necessarily first generation) of the original negative, which can be used as the source for duplicate copies.

Internal accuracy: The measurement of the precision or bit-depth that a software package uses to represent and modify image data.

International Color Consortium: The organization established for the purpose of standardizing color management across different platforms.

Interocular distance: The spacing b etween the eyes, usually referring to the human average of about 2lhinches; an important factor for the production of stereoscopic imagery.

Interpolation: The process of using certain rules or formulas to derive new data based on a set of existing data. See also bicubic interpolation, bilinear interpolation, linear interpolation.

Interpositive (IP): Short for intermediate positive, a positive print made from the original negative for use in making internegatives.

Inverse kinematics: Often abbreviated to IK, Inverse Kinematics is a character animation technique in which the end bone of a chain – for example, a limb – is assigned a goal object. When the goal object moves, the bone moves with it, dragging the rest of the chain behind it. The movement propagates from the free end of the chain towards the fixed point: the reverse of Forward Kinematics.

ISO index: A standard numerical rating for specifying a film’s sensitivity to light. “ISO” refers to the International Standards Organization. The ISO Index actually incorporates both the American ASA rating and the European DIN rating. Many manufacturers now use their own specific exposure index instead. See also ASA rating, DIN rating.

Isoparm: Lines on a NURBS surface connecting points of constant U or V co-ordinate values, and representing crosssections of the NURBS surface in the U or V directions.

J

JPEG: A (typically lossy) compression technique, or a specific image format that utilizes this technique. “JPEG” is an abbreviation for the Joint Photographic Experts Group.

K

Kernel: The group of pixels that will be considered when performing some kind of spatial filtering. See also convolution kernel.

Key: Another term for a matte.

Keying: The process of algorithmically extracting an object from its background and combining it with a different background.

Keyframe: Any frame in which a particular aspect of an item (its size, location, color, etc.) is specifically defined. The non-keyframe frames will then contain interpolated values.

Keyframe animation: The process of creating animation using keyframes.

Keyframing: Another term for keyframe animation.

Keystoning, keystone distortion: A geometric distortion resulting when a rectangular plane is projected or photographed at an angle not perpendicular to the axis of the lens. The result is that the rectangle becomes trapezoidal.

Kukaloris: See cukaloris.

L

Lens artifact: Any artifact, such as a lens flare or chromatic aberration, that appears in an image as a result of the lens assembly.

Lens flare: An artifact of a bright light shining directly into the lens assembly of a camera.

Letterboxing: A method for displaying images that preserves the aspect ratio ofthe film as it was originally shot, using black to specify areas outside of the original frame.

Light pass: (1) In multipass photography, the pass of individual lights striking the subject, such as the key or fill, for later use in compositing. (2) In multiple-pass rendering, the CG element that represents the effects of a particular light striking the object.

Lighting reference: A stand-in object that can be used to judge the lighting in a scene.

Linear color space: A color space in which the relationship between a pixel’s digital value and its visual brightness remains constant (linear) across the full gamut of black to white.

Linear interpolation: A method of interpolation that is based on the average of the two nearest neighbors. See also bicubic interpolation, bilinear interpolation.

Linear space: See linear color space.

Locked cut: Term meaning that no more editing will be done on the shot, scene, or project; the edit is 100% complete.

Locked-off camera: A camera whose position and lens settings do not change over the duration of the shot.

Log space: An abbreviation for logarithmic color space, a nonlinear color space whose conversion function is similar to the curve produced by the logarithmic equation.

Long lens: A relative term, in contrast to a short lens. Also known as a telephoto lens.

Look-up table: A method of mapping input colors to output colors. Instead of using an algorithm to define the color modification, a table of values is created so that every possible input color will have an output value defined.

Lossless compression: A method of compressing and storing a digital image in such a fashion that the original image can bc completely reconstructed without any data loss.

Lossy compression: A method of compressing and storing a digital image in such a fashion that it is impossible to perfectly reconstruct the original image.

Low-pass filter: A spatial filter that removes high-frequency detail. It is used as a method for blurring an image.

Luminance: In conunon usage, synonymous with brightness. In the HSL color space, luminance is the weighted average of the red, green, and blue components.

Luma-keying: A matte-extraction technique that uses the luminance values in the image.

LUT: Abbreviation for look-up table.

LZW compression: A lossless compression method that finds repeated patterns in blocks of pixels in an image. Variations of LZW compression are used in a number of image file formats, including GIF and TIFF. “LZW” stands for Lempel-Ziv-Welch.

M

Mach banding: An optical illusion (named after the physicist Ernst Mach) in which the eye perceives emphasized edges in areas of color transition. This illusion causes the eye to be more sensitive to contouring artifacts. macro: (1) In the digital world, a combination of functions or effects that are grouped together to create a new effect. (2) A specialized lens that is capable of focusing at an extremely close distance to the subject.

Macro: (1) In the digital world, a combination of functions or effects that are grouped together to create a new effect. (2) A specialized lens that is capable of focusing at an extremely close distance to the subject.

Mandrel: Form to replicate the volume and basic shape of an object for on-set interaction. The actual image of the object will be added in post-production.

Mask: An image used to selectively restrict or modify certain image processing operations on another image.

Matchmove: The process of extracting the camera move from a live-action plate in order to duplicate it in a CG environment. Often performed by hand as opposed to 3D tracking in which software is used to help automate the process.

Matte: An image used to define or control the transparency of another image. See also articulate matte, complementary matte, difference matte, edge matte, fixed matte, garbage matte, G-matte, hold-out matte, rotoscoped matte, static matte, traveling matte.

Matte channel: Another name for the alpha channel in a four-channel image.

Matte extraction: Any process used to create a matte.

Matte line: An artifact of the matting process wherein a foreground element has a noticeable outline.

Matte painting: A hand-painted image, usually intended to be photorealistic, that is combined with live-action footage.

Matte pass: (1) In multiple-pass photography, a pass that is lit in some high-contrast fashion so that it can be used as a matte during compositing. (2) In multiple-pass rendering,  a separate render of the alpha channel of one of the objects in the scene for use during compositing.

Maximum density: The point of exposure at which additional light (on the negative) will no longer affect the resulting image. The definitions of maximum and minimum density would be reversed if you were speaking of print (reversal) film instead of negative. Also known as D-max.

Median filter: A specialized spatial filter that removes pixel anomalies by determining the median value in a group of neighboring pixels.

Minimum density: The point of exposure just below the amount needed (on the negative) to start affecting the resulting image. The definitions of minimum and maximum density would be reversed if you were speaking of print (reversal) film instead of negative. Also known as D-min.

Mitchell filter: A specific digital filter that is often used when resampling a digital image. The Mitchell filter is particularly well suited to transforming images into a higher resolution than they were originally.

MoCap: Abbreviation for motion-capture. Also known as performance capture.

Moco: Abbreviation for motion control.

Monochrome: An image that contains only a single hue, and the only variation is in the luminance of that hue. Typically, a monochrome image consists only of shades of gray.

Morphing: A process in which two image sequences are warped so that key features align as closely as possible and then a selective dissolve is applied to transition from the first sequence to the second. The result should be a seamless transformation between the two sequences.

Motion artifact: A general term describing all forms of image artifacts due to motion, such as strobing or wagon wheeling.

Motion blur: An artifact caused by the fact that a camera’s shutter is open for a finite duration as it captures an image. Any object that is moving during that time will appear blurred along the path that it was traveling.

Motion control: A method of using computer-controlled mechanisms to drive an object’s movement so that it is continuously repeatable.

Motion-control camera: A camera whose position, orientation, and lens settings are motion controlled.

MPEG: A (typically lossy) compression technique specifically designed to deal with sequences of images, or the format of the images produced by this technique.”MPEG” is an abbreviation for the Moving Pictures Experts Group.

Multimedia: A broad categorization that generally refers to some method of displaying information using sound and imagery simultaneously.

Multiplaning / multiplane compositing: A technique that simulates a moving camera by translating the different layers in a composite by an amount that is appropriate to their intended distance from this camera. Layers that are intended to appear farther away are moved by a smaller amount than layers that are intended to be nearer, producing a simulated parallax effect.

Multiple-pass photography: Any filming in which multiple exposures of the same subject are filmed, generally with different lighting setups. If the camera is moving then it must be motion controlled to ensure accurate alignment between passes. Typical passes include a beauty pass, matte pass, reflection pass, and shadow pass.

Multiple-pass rendering: A technique in which a 3D object or scene is rendered in a series of separate images, each with different lighting or rendering characteristics. Typical passes might include color, shadow, reflection, key light, fill light, backlight.

N

Naming conventions: The standardized names that are used within a project to differentiate the various elements and files that are stored on disk during production.

ND filter: See neutral density filter.

Nearest-neighbor filter: Another term for the impulse filter.

Neutral density filter: An optical filter that is designed to reduce the intensity of the light passing through it without affecting the color of the light.

Newton’s rings: An artifact, usually seen in optical printing, characterized by circular moire patterns that appear in the image.

NG: Abbreviation for “no good.”

Nodal camera: A camera that can pan, tilt and and roll without creating any parallax shift between foreground and background. Typically a mounted camera.

Nonlinear color space: A color space in which the relationship between a pixel’s digital value and its visual brightness does not remain constant (linear) across the full gamut of black to white.

Nonlinear editing: Editing that does not require that the sequence be worked on sequentially.

Nonsquare pixel: A pixel whose width is not the same size as its height. The ratio of width to height is measured in terms of a pixel aspect ratio.

NTSC: National Television Systems Committee. Refers not only to the committee itself, but also to the standard that they established for color television in the United States and other countries. It carries 525 lines of information, played back, at a rate of approximately 30 frames per second (actually 29.97). Due to its unreliable color reproduction ability, the initials are often said to stand for “Never The Same Color” or “Never Twice the Same Color.”

NURBS: Abbreviation for nonuniform rational B-spline.

O

Occlusion: State in which objects, or portions of objects, are not visible because they are blocked by other objects or portions of objects.

Off-line compositing: Another term for batch compositing.

Omnimax: A proprietary film capture/projection process that uses the same large-format negative as the IMAX process but is designed for projection on the interior of a dome-shaped screen.

On-line compositing: A method of compositing that uses a highly interactive hardware/ software combination to quickly provide the results of every compositing operation. Distinguished from an off-line or batch compositing system.

Opaque: The characteristic of an image that causes it to fully obscure any image that is behind it. Opaque is the opposite of transparent.

OpenEXR: A specific image file format designed for use with high dynamic range imagery.

OpenGL: Abbreviation for open graphics library.  A standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. Programs that use OpenGL can leverage graphics cards to accelerate graphics.

Optical compositing: The process of using an optical printer to produce composite imagery.

Optical flow analysis: A method for procedurally determining the movement of objects in an image by examining the full sequence from which the image was extracted.

Optical printer: A device used to combine one or more different film elements and rephotograph them onto a new piece of film.

Orthographic: Representing a 3D object in two dimensions.

Overcranked: Footage shot at a faster-than-normal rate is said to have been shot overcranked.

Oversampling: Sampling data at a higher-than-normal resolution in order to mitigate sampling errors or inaccuracies from uncharacteristic data.

P

Paintbox: Usually used in the video postproduction world as a generic term for a variety of paint and compositing devices.

Paint software: A program that allows the artist to “paint” directly onto an image in the computer using a device such as a tablet or a mouse.

PAL: Phase alternation by line. A standard for color television found in many European, African, and Asian countries. It carries 625lines of resolution, played back at a rate of 25 frames per second.

Palette: The range of colors available for use in any particular application. A system that uses eight bits per channel would have a palette of over 16 million colors.

Pan and scan: A technique that is used to convert images shot with a widescreen film process to a less expansive video format. It generally involves selectively cropping the image to fit into the new frame, arbitrarily choosing what portions of the image are unnecessary.

Pan and tile: A technique in which a series of images of a scene are stitched together to create a larger panoramic view of the scene.

Panavision: (1) A manufacturer of motion picture lenses and cameras. (2) The trade name for a specific wide screen process and lenses developed by the Panavision company. It is an anamorphic format that produces an image with a 2.35:1 aspect ratio. See also anamorphic format, Cinemascope.

Parallax: The perceptual difference in an object’s location or spatial relationship when seen from different vantage points.

Particle system: A 3D computer graphics technique that is used to create a large number of objects that obey well-defined behavioral rules. Useful not only for controlling multitudes of discrete objects such as asteroids or flocks of birds, but also as a tool for creating natural phenomena such as fire or smoke.

Peg registered: Special animation paper wiht special holes that fit over animation pegs on an animation stand /table to ensure proper registration of the paper. Also used with animation cells.

Perf: Abbreviation for perforation.

Perforation: One of the sprocket holes that runs along the edges of a piece of film. They are used to guide the film reliably through the camera.

Periwinkle effect: Technique for shooting wet-for-dry using an underwater bluescreen process.

Persistence of vision: The characteristic of the human eye that allows it to continue to perceive an image for a fraction of a second after it disappears.

Perspective: A term relating to the size and depth relationships of the objects in a scene.

Perspective compensation: The use of a two-dimensional geometric transformation to correct a 3D discrepancy.

Photogrammetry: A method in which textured 3D geometry is created based on the analysis of multiple 2D images taken from different viewpoints.

Photorealism: a global term used to describe CG images that cannot be distinguished from objects or scenes in the real world.

Picture element: See pixel.

Pincushion distortion: A type of lens distortion in which straight lines are bent inward toward the center of an image. Also called barrel distortion.

Pipeline: A well-defined set of processes for achieving a certain result.

Pixel: Originally an abbreviation for “picture element,” although the term “pixel” is generally considered to be a true word nowadays. A digital image is composed of a rectangular array of individual colored points. Each one of these points is referred to as a pixel.

Pixel aspect ratio: The width of a given pixel divided by its height. A number of image representation methods do not use pixels that have an equivalent width and height. The pixel aspect ratio is independent of a particular image’s aspect ratio. See also nonsquare pixels.

Pixelation animation: Stop-motion technique in which live actors are used as a frame-by-frame subject in an animated film by repeatedly posing while one or more frame is taken and changing the pose slightly before the next frame or frames.

Plate: A piece of original photography that is intended to be used as an element in a composite.

Playback speed: The rate (usually measured in frames per second) at which a sequence of images is displayed.

Polygon: A geometry element formed by connecting three or more points. A triangle, or three-point polygon, is the simplest form of polygonal geometry. Polygonal modelling is a fast, intuitive method of creating 3D objects, but does not easily generate smooth curved surfaces.

Posterization: An effect applied to an image that intentionally causes banding.

Postproduction: Work done once principle photography has been completed.

Practical effects: Effects that are accomplished “live,” without any postproduction. Practical effects include explosions, artificial rain, smoke, etc.

Precomp: Abbreviation for preliminary composite.

Preliminary composite: (1) Any intermediate imagery that is produced during the digital compositing process that can be saved and used as a new source element. (2) A quickly assembled composite that is designed to show the relationship of various photographic elements to determine if any of these elements needs to be reshot.

Premultiplied image: An image whose red, green, and blue channels have been  multiplied by a matte. Usually this matte is stored as the alpha channel of this image.

Preproduction: Any planning, testing, or initial design that is done before actual production begins.

Previs: Abbreviation for previsualization.

Prime lens: A camera lens with a fixed focal length as opposed to a zoom lens, which has a variable focal length.

Primatte: A proprietary chroma-keying tool that can be used to extract a matte from an image shot in front of a uniform backing.

Print: A positive image that is suitable for viewing directly or for projection. Generally produced from an original negative.

Procedural paint: A specialized form of paint software that can actually apply brush strokes and other paint processes over a sequence of images instead of just a single frame. Parameters for these painting effects can usually be animated as well.

Procedural texture: A texture map that is generated by a mathematical function, rather than a real-world bitmap image projected over the surface of an object.

Processing: (1) The time spent by the computer as it computes any instructions that it has been given. (2) At a photo laboratory, the process of developing and printing a piece of film.

Producer: Administrative head of a project. Responsible for budget, schedule, etc.

Production sense: The near-mythical ability of an experienced digital artist to decide on the proper course of action when creating a visual effects shot.

Progressive scan: A method of displaying an image that does not rely on interlacing.

Projection speed: The playback speed for projected imagery.

Proxy: A scaled-down image that is used as a stand-in for a higher-resolution original.

Pull a matte: The process of creating a matte for an object, usually through keying techniques.

Pulldown: Shorthand for 3:2 pulldown

Pullup: Shorthand for 3:2 pullup

Q

Quantization: The process of assigning discrete digital values to samples taken from a continuous analog data set.

Quantization artifact: A term generally used to refer to a visually noticeable artifact of the quantization process.

Quantizing: Colloquial term for a quantization artifact.

R

Radiosity: A technique for rendering 3D scenes. Radiosity simulates the way in which light bounces from surface to surface within a scene, and is more accurate, but also more processor intensive, than raytracing.

Raster graphics: Image representation using a grid of pixels while vector graphics use line information.

Raw stock: Unexposed, unprocessed film.

Raytracing: A technique for rendering 3D scenes. Raytracing traces the path of every ray of light from its source until it either leaves the scene or becomes too weak to have an effect. The term is also sometimes applied to the reverse method: tracing the path of every ray of light from the camera backwards to the light source.

Real-time: (1) Displaying a sequence of images at the same speed as they will be viewed in their final form. (2) Computational processing that appears to be nearly instantaneous.

Rear projection: A compositing process in which the previously photographed background scene is projected onto a large translucent screen from behindnwhile the foreground action takes place. The composite is thus considered an in-camera effect.

Record: One of the red, green, or blue color-sensitive layers in a piece of film. Thus, the “blue record” is equivalent to a digital image’s blue channel. region of interest: A (usually rectangular) region that is determined by the user in order to limit certain calculations. See also domain of definition.

Reference spheres: Chrome and neutral gray globes, used on the set to virtually record the placement of lights within a scene. CG artists later use the sphere9s) reference as a guide for placing CG lights to help make CG and live-action objects appear to be in the same environment.

Reflection map: An environment map used to simulate real-world reflection effects on the surface of a 3D object. Reflection maps render more quickly than methods that generate true surface reflections, such as raytracing.

Release print: A print of a movie that will be sent to theaters for display. A  release print is several generations removed from the original negative.

Render: The process of creating a synthetic image from a 3D database.

Render farm: A group of computers that is set UP as a place to submit 2D or 3D processes for non-interactive computation.

Render queue: The list of tasks waiting to be processed on a render farm.

RenderMan: Specialized rendering software offered by Pixar, Inc.

Repo: See reposition.

Reposition: The process of adjusting the placement of an element within the frame.

Resampling: The process of reading previously sampled data for the purpose of converting or modifying it.

Resolution: The amount of data that is used to capture an image. The term is typically used to refer specifically to the spatial resolution of a digital image. See also color resolution, temporal resolution.

Resolution independence: The characteristic of a software package that allows the user to easily work with and move between an arbitrary number of different resolutions.

RGB: Red, green, and blue. The three primary colors, or a method of specifying the colors in an image based on a mix of these three components.

Ride film: A location-based entertainment that features a film whose camera movements are synchronized with some sort of moving scat or platform.

Rigging: The process of preparing a character model for animation, including setting up an underlying skeleton, complete with constraints, controllers and kinematic systems, and linking it to the mesh of the character model.

Rigid-Body Dynamics: simulate the physical behaviour of rigid objects that do not deform upon collision.

Ringing: A visual artifact, often caused by excessive sharpening, that is characterized by overemphasized transitions between bright and dark areas in an image.

RLA: A specific image file format.

ROI: Abbreviation for region of interest. Also used in the financial world as an abbreviation for Return On Investment, something your employer is probably worrying about right now.

Rotation: A geometric transformation that changes the orientation of an image relative to a certain axis.

Rotoscope: Originally the name of a device patented in 1917 by Max Fleischer to aid in cel animation. Now used as a general term for the process of creating imagery or mattes on a frame-by-frame basis by hand.

Rotoscoped matte: A matte created via rotosc::~ping techniques.

RP: Abbreviation for rear projection.

RTFM: Abbreviation for “read the manual” (sort of), a s:;ggestion that is often given when someone asks a question instead of taking the time to look it up themselves.

Run-length encoding: A lossless compression scheme that consolidates sequences of identical pixels into a single data representation.

Rushes: Another term for dailies, used primarily in Great Britain.

S

Sampling: (1) The process of reading a signal at specific time increments. See also digitization. (2) The process of reading the color value from a pixel or a group of pixels.

Saturation: The brilliance or purity of a given color. The difference between a pastel and a pure color is the amount of saturation.

Scaling: A geometric transformation that changes the size of an image, usually without changing its location or orientation.

Scan line: A single horizontal row of pixels in a digital image.

Scanline render: 

Scanner: A device for digitizing film, print material, etc.

Scene: (1) The image captured by a camera. (2) A collection of shots that share a common setting or theme.

Scope: Abbreviation for Cinemascope.

Screen resolution: The number of horizontal and vertical pixels that a given display device is capable of showing. This should be independent of the resolution that the system is capable of processing.

Script: A program written in a scripting language, including the language used by a compositing package to describe the set of image-processing operations to be applied to a set of images.

SDK: Abbreviation for software developer kit.

SECAM: Officially this is an acronym for sequentiel couleur a memoire, but most English speakers use the translation “sequential color and memory.” A standard for color television used in France and a few African and Eastern European nations. It carries 625 lines of resolution, played back at a rate of 25 frames per second. Also stands for Something Essentially Contrary to AMerica.

Seed: A number that is fed into a program or algorithm to produce a random number. The same seed will result in the same random numbers and therefore can provide for repeatable iterations.

Sequence: (1) A collection of images designed to be played sequentially. (2) A group of related scenes in a film, usually set in the same time and/ or location.

Server: A computer that is shared over a network by several users.

SFX: Often used as an abbreviation for special effects, although sound effects people will dispute this usage.

Shading: The mathematical process of calculating how a model’s surfaces react to light. A variety of alternative algorithms can be used for the task, including Phong, Lambert, and Blinn
shading models. Shaders are often built up as node-based shading trees, with each node controlling a specific aspect of the process.

Sharpening: The process of applying an algorithm that emphasizes the edges in an image. The result is an image that appears to have increased sharpness.

Sharpness: The visual sense of the abruptness of an edge.

Short lens: A relative term, in contrast to a long lens. Also known as a wideangle lens.

Shot: An unbroken continuous image sequence.

Showscan: A proprietary film capture/projection process that is characterized by a large-format negative and a playback speed of 60 frames per second.

Shutter angle: The part of a motion picture camera that determines how long a given area of film will be exposed to a scene. Most cameras have the ability to adjust their shutter angle. A larger shutter angle will result in increased motion blur on moving objects.

Shutter speed: The amount of time that a camera will spend capturing an individualimage.

SIGGRAPH: The Special Interest Group for Graphics, a subgroup under the Association for Computing Machinery; and the major organization for graphics professionals. Also, the annual conference sponsored by this group, which features a large number of courses, seminars, and really big parties.

Sinc filter: A specific digital filter that is often used when resampling a digital image. The sine filter is particularly well suited to transforming images into a lower resolution than they were originally.

16-bit image: any image containing 16-bit of information per channel.

Skip frames: A method of speeding up the motion of a sequence of images by removing selected (usually regularly spaced) frames. Also known as skip printing.

Slate: Information about a particular shot that is placed at the head of the shot, before the actual image begins.

Slop comp, slap comp: A very rough initial composite that is usually used to test or visualize basic element relationships.

Slow-mo: Abbreviation for slow motion.

Slow motion: Imagery that was filmed at a faster speed than it is to be projected. The result is a sequence that appears to be moving slower than normal.

SMPTE: Society of Motion Picture and Television Engineers.

Solarization: An effect that is produced when a range of brightness within an image is inverted. Can be used to mimic an optical effect that occurs with extreme overexposure.

Spatial aliasing: An artifact that is due to limited spatial resolution.

Spatial convolution: See convolve.

Spatial filter: A method of sampling and modifying the data in an image by looking at pixel groups.

Spatial resolution: A measurement of the amount of data used to capture an image. In a digital image, spatial resolution is usually specified by giving the X and Y dimensions of the image as measured in pixels.

Special effects: A term used to encompass both practical effects and visual effects.

Special visual effects: See visual effects.

Specular:

Spherical lens: A lens that does not change the apparent width-to-height relationship of the scene being photographed. This is in contrast to an anamorphic lens.

Spill: Any light in a scene that strikes an object it was not intended to illuminate. See also blue spill, green spill.

Spline curve: A continuous smooth curve defined by a certain number of control points.

Split-screen: A basic composite in which two elements are combined using a simple matte with little or no articulation.

Square pixel: A pixel with equal X and Y dimensions.

Squeezed image: An image that has been anamorphically compressed.

sRGB: A standard RGB color space created cooperatively by HP and Microsoft in 1996 for use on monitors, printers and the Internet.

Stabilization: The process of removing bounce or jitter from a sequence of images.

Staircasing: A spatial aliasing artifact in which a line or edge appears jagged, like the profile of a staircase, instead of smooth.

Stand-in: A reference object photographed in a particular scene that can later be used to help match the color and lighting of any new elements that will be added to that scene.

Static matte: Another term for a fixed matte.

Steadiness: An image sequence in which the individual frames are stable relative to each other and do not suffer from any frame-to-frame jitter or bounce.

Steady test: A test to determine if a camera or the imagery shot with that camera is steady.

Stereoscopic imagery: Imagery that is designed to send a different image to each observer’s left and right eyes, thereby producing a sense of depth.

Stochastic sampling: A random or semirandom sampling of a data set. Used for antialiasing, motion blur, etc.

Stock: General term for motion picture film, or the specific manufacturer, manufacturer’s  product code, or rating of that film.

Stop: A way of measuring exposure that traces back to the different £-stop settings available on any given lens. F-stops on a lens are calibrated so that each successive stop will give twice the exposure. Thus, “increase the brightness by one stop” means to double the brightness; “decrease by two stops” would result in one-fourth the original brightness.

Stop-motion animation: An animation technique that involves photographing miniature objects or characters a frame at a time, changing the pose or position of the object between each frame. The result, when played back at normal speed, is of a continuously animating object.

Storyboard: A sequence of drawings that shows the intended action in a scene. Used as a visualization tool before the scene is shot.

Strobing: A rhythmic flicker in a moving image.

Subblack: see Superblack

Subpixel: Any technique that works at a resolution of greater than a single pixel, usually accomplished by making slight weighted corrections to several surrounding pixels.

Super: Abbreviation for superimpose.

Superblack: Any brightness level that drops below the normal representation of black for a given image or device. In video, superblack levels may be used for keying.

Superimpose: To place one image on top of another, usually with some transparency involved.

Super 35: A specific 35mm film format. .

Superwhite: Any brightness level that rises above the normal representation of white for a given image or device.

Surface normal: A vector that is perpendicular to a surface at a specific point on the surface.

T

Tablet: A user-input device that provides a greater amount of control thanthe traditional computer mouse. Generally used in conjunction with a specialpen.

Tail slate: Slate information that is recorded at the end of the shot instead of the beginning. Generally only used in live-action photography; the slate information is filmed upside-down, to distinguish it from a normal slate.

Take: When a particular shot is photographed multiple times in order to achieve a desired result, each time is referred to as a “take.” This concept extends to digital compositing, where each test that is sent to film or video is usually kept track of by a “take number.”

TARGA: A specific image file format.

Telecine: A device for rapidly converting motion picture film into a video format. Some newer telecine devices will convert to HDTV resolutions as well. A telecine device is much faster than a film scanner, but will produce lower quality results.

Telephoto lens: Any lens that has a longer-than-normal focal length. For a 35mm camera, a focal length of 50mm is considered normal, since it reasonably duplicates the magnification of a human eye.

Temp comp: See temporary composite.

Temporal: relating somehow to time or something that changes over time.

Temporal aliasing: An artifact that is due to limited temporal resolution.

Temporal resolution: A measurement of the amount of data used to capture a sequence of images. Temporal resolution is usually specified by giving the number of frames per second used to capture the sequence.

Temporary composite: A rough composite produced for a number of different reasons, usually to better judge the spatial and color relationships of the elements in a scene so that they can be modified to produce a final composite.

Tesselation: (1) A collection of plane figures that fills the plane with no overlaps and no gaps.

Texture mapping: Process in which an image is overlaid onto a CG object.

Texture: A bitmap image that is applied to the surface of 3D object to give it detail. Texture maps may be either photographic images or procedural textures, and may be applied in each of the material channels of an object using a variety of mapping or projection methods.

TGA: See TARGA.

3D graphics: Computer graphics that involves the creation of three-dimensional models within the computer.

32-bit image: Any image containing 32-bit of information per channel. At this bit-depth the channels are usually stored with a floating point data representation. Also referred to as a float image.

3:2 pulldown: Usually synonymous with 2:3 pulldown.

3:2 pullup: Usually synonymous with 2:3 pullup.

TIFF: Tagged Image File Format, a specific image file format.

Time code: An electronic indexing method used with video tapes. Time code is measured in hours, minutes, seconds, and frames.

Timeline graph: A graph that represents the temporal relationships between objects or data.

Timing: (1) A general term referring to how a particular event or object moves or evolves over a period of time. (2) See color timing.

Tracking: The process of selecting a particular region of an image and determining that region’s movement over time.

Transformation: Usually refers to a geometric transformation.

Transition effect: A method for moving from one scene to the next. See also wipe, dissolve.

Translation: A geometric transformation that refers only to a change in position, without a change in scale or rotation.

Translucent: A term that refers to something that is partially transparent; usually implies some additional image distortion, such as blurring.

Transparent: The characteristic of an image that allows other images that are behind it to still be partially visible. Transparent is the opposite of opaque.

Traveling matte: Any matte that changes over time, as opposed to a static matte.

Trucking: Camera movement that is perpendicular to the lens direction.

T-stop: A measurement of the aperture of a lens that also takes into account the amount of light lost when passing through the lens elements themselves.

2D graphics: Computer graphics that does not use any 3D techniques and thus involves no explicit depth information.

2:3 pulldown: A method for converting 24-fps film to 30-fps video.

2:3 pullup: A method for converting 30-fps video to 24-fps film.

U

Ultimatte: A proprietary tool based on the color difference method that can be used to extract a matte from an image shot in front of a uniform backing.

UNIX: A powerful operating system developed in the 1960s. It is most popular on high-end workstations, although an excellent variant, LINUX, is available for a number of platforms, including PCs.

Unpremultiplied image: An image whose RGB channels have not been multiplied by an alpha channel.

Unpremultiply: To devide the RGB channels by the alpha channel.

Unsharp masking: A particular technique used to sharpen an image that involves subtracting a slightly blurred image from the original. Used not only in the digital realm but also as a photographic technique.

Unsteadiness: Not possessing the characteristic of steadiness.

User interface: The portion of a computer program that deals specifically with how the user interacts with the software. See also graphical user interface.

UV texture co-ordinates: The co-ordinate system used for assigning textures to polygonal models. Since UV co-ordinate space is two-dimensional, one of several projection methods must be used to ‘unwrap’ the UVs from the model and lay them flat on a plane. Once unwrapped, the UV map may be screengrabbed and exported to a paint package for texture painting.

V

Value: In the HSV color space, the value equals the maximum of the red, green, and blue components.

Vaporware: A product that does not yet exist, but is nevertheless being promised for delivery.

Vector graphics: Geometrical primitives, such as points, lines curves and shapes or polygons, that are based on mathematical equations that represent images in computer graphics.

VFX: Abbreviation for visual effects.

VHS: A video recording format that carries a pathetic 240 lines of resolution.

Vignetting: A camera or lens artifact characterized by a darkening of the image in the corners of the frame.

Vista Vision (or Vistavision): A specialized 35mm film format that runs the film through the camera horizontally instead of vertically and is able to capture more than twice the resolution of a standard 35mm frame. Generally only used for visual effects work nowadays. Also known as eight-perf.

Visual effects: A broad term that refers to just about anything that cannot be captured using standard photographic techniques. Visual effects can be accomplished in-camera or via a number of different optical or digital post-production processes. Visual effects are a subcategory of special effects.

Visual effects producer: The individual responsible for the administrative side of visual effects production.

Visual effects supervisor: The individual responsible for the creative and technical side of visual effects production.

W

Warm: A nonexact term used to describe an image that is biased toward the red portion of the spectrum.

Warping: A geometric, per-pixel distortion of an image, often based on some kind of spline- or grid-based control.

Warping engine: Within a package used for compositing, the code that is responsible for any geometric transformations.

Weave: See film weave.

Wedge: See color wedge, exposure wedge.

White point: (1) On a piece of film, the measured density in the area of least opacity. (2) In a digital image, the numerical value that corresponds to the brightest area that will be represented when the image is eventually viewed in its final form.

Wide-angle lens: Any lens that has a smaller-than-normal focal length. For a 35mm camera, a focal length of 50mm is considered normal, since it reasonably duplicates the magnification of a human eye.

Widescreen: A generic term that usually refers to any image with an aspect ratio greater than 1.33:1.

Wipe: A specific transition effect in which one scene is horizontally or vertically revealed to replace another scene.

Wire removal: A generic term for the process of using digital painting or compositing techniques to remove undesirable wires, rigs, or harnesses that were needed to aid certain stunts or practical effects.

Witness points: Specific objects placed into a scene that can later be analyzed to determine the movement and configuration of the camera that photographed the shot.

Working resolution: The resolution of the images that will be produced by any given compositing process.

X

X: An abbreviation used to denote a frame. “24x” denotes 24 frames.

X-axis: Generally the horizontal axis.

Y

Y-axis: Generally the vertical axis.

YIQ: A color space used for NTSC television, in which the brightness (Y), orange-cyan (I), and green-magenta (Q) components are encoded together.

YUV: A color space in which Y represents the luminance and U and V represent the chrominance of an image.

Z

Z-axis: The axis perpendicular to the X-axis and the Y-axis, and consequently the axis that is used to represent depth.

Z-buffer: Another term for a Z-depth image.

Z-channel: A Z-depth image that is integrated with a color image as an additional channel.

Z-depth compositing: Compositing images together with the use of a Z-buffer to determine their relative depths, or distances from the camera.

Z-depth image: A specialized image that uses the brightness of each pixel to specify the relative depth for each pixel in the corresponding RGB image. This depth may be measured relative to some arbitrary fixed point in space or relative to the virtual camera that is being used to capture the scene.

Zoom: (1) In a real camera, to increase the focal length of the camera’s lens, magnifying a portion of the scene. (2) With digital images, to increase the scale of a portion of an image in order to duplicate the effect of a camera zoom. information, as opposed to blanking, closed-captioning, time code, etc.

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