The following is a selected glossary of terms relating to electronic media. The source of each definition is identified in parentheses. All definitions are reprinted with the permission of the authors. (See "Glossary Sources" below for information about the sources.)

A/B Roll - The use of alternating scenes, recorded on separate videotape reels (an A roll and a B roll), to perform dissolves, wipes or other types of video transitions. [BAVC]

Access points - A database field or metadata category designed to be searchable and retrievable by an end-user. Also used to denote a place where wireless network access is available. [Getty]

Access storage - Storage conditions at or near room ambient conditions that allow tape collections to be readily accessed for immediate playback. "See also Archival storage" [AMIA]

Acclimatization areas - A room or storage space that allows film, recordings and other material to adjust between ambient conditions [i.e. room temperature] and cold, dry storage, with minimal stress, and without condensation forming. The process may last days or weeks. [MIC]

Aliasing - Jagged edges along the outer edge of objects or text. Anti-aliasing refers to software adjustments that correct this effect. This effect is created by inadequate sampling techniques in computer-produced images. [Projector People]

Ambient light - Any light in the viewing room created by a source other than the projector or screen. [Projector People]

Ambient sound - A representative sample of background audio (such as a refrigerator hum or crowd murmur) particular to a shooting location. Ambient sound is gathered in the course of a production to aid the sound editor in making cuts or filling in spaces between dialog. Also called Room tone. [BAVC]

Ampex DCT (Digital Component Tape) - Compressed, 10-bit digital component format with similar specifications to Digital Betacam but not as popular. Introduced by Ampex in 1993. Cassette sizes and running times same as D-2, 13 micron tape thickness. Many users of this format claim that it has the best quality of the compressed formats. Machines are solidly built with gentle tape handling, and many are still in use ten years after their introduction. [MIC]

Analog - A continuously varying electronic signal. Audio and video analog signals stored on tape deteriorate with each copy or generation. In contrast see digital. [BAVC]

Analog recording - A recording in which continuous magnetic signals are written to the tape that are representations of the voltage signals coming from the recording of the video camera or microphone. Analog signals stored on tape deteriorate with each copy or generation; in contrast see digital. [BAVC]

Analog video - A system of recording video images that employs continuously varying waveforms to encode brightness, color and the timing information necessary to reproduce a moving image. [BAVC]

Analog-to-digital - The process in which a continuous analog signal is quantized and converted to a series of binary integers. [BAVC]

Annotation - Commentary added to a media object, generally providing explanatory information or editorial notes regarding the media file. Annotations are a form of metadata [Getty]

ANSI - The American National Standards Institute has served in its capacity as administrator and coordinator of the United States private sector voluntary standardization system for 78 years. Founded in 1918 by five engineering societies and three government agencies, the Institute remains a private, nonprofit membership organization supported by a diverse constituency of private and public sector organizations. [ScreenSound Australia]

ANSI Lumens - ANSI stands for American National Standards Institute. It is a standard for measuring light output. Different lamps play a role on light output. Halogen lamps appear dimmer than another metal-halide, even if the two units have the same ANSI lumen rating. Type of LCD technology (active matrix TFT, Poly-Si, passive), type of overall technology (LCD vs. DLP vs. CRT), contrast ratios, among other factors can also affect the end result. [Projector People]

Archival format - A video format that provides reliable playback, without information loss. The format should be a current (as opposed to obsolescent) professional one supported by the industry. At present archival video material is typically stored on magnetic tape however in the near future computer-based storage is likely to become an option for archives. The advantage of uncompressed digital formats over analog formats is that they can be copied without generational loss. For this reason many archives are using digital formats for creating their archival masters. Ideally these formats should be uncompressed, component formats; however, for practical and cost reasons formats employing lossless compression are also used. Suitable archival formats will change as older formats become obsolete and are no longer supported. Ideally, archival master material is transferred onto new stock every 5-7 years and at this point a decision should be made about whether it is necessary to move to a new format as well. An archival format is therefore one that can be migrated onto new stock and new formats without the loss or distortion of information. [BAVC]

Archival storage - Storage conditions specifically designed to extend or maximize the lifetime of stored media. Generally characterized by levels of temperature and relative humidity lower than those in access storage conditions and with minimal fluctuations. Access to archival storage by personnel is limited for security reasons. [AMIA]

Artifact - An undesirable picture element in a video image, which may naturally occur in the recording process and must be eliminated in order to achieve a high quality image. Most common artifacts are cross-color and cross-luminance. [BAVC]

Aspect Ratio - Aspect ratio refers to the relationship or ratio between the width of the image and the height of the image. There are two standard aspect ratios: 4:3 and 16:9. A standard TV has an aspect ratio of 4:3, which means that the picture is four units wide for every three units of height. HDTV standard is 16:9, which is 16 units of width for every 9 units of height. [EAI]

ASTM - American Society for Testing and Materials [BAVC]

Audio - The sound portion of a program. [BAVC]

Audio mixer - A component that combines more than one sound input for composite output. [BAVC]

Authoring program - Software designed to help a nonprogrammer write source code, typically through a menu-driven or graphical interface. [Variable Media]

Authority/authority file - A file or set of terms extrinsic to records describing objects or documents. A more efficient way of recording information, which need be recorded only once and may then be linked to all appropriate records. [Getty]

Avatar - A virtual representation of a user on a network, typically in text or graphic form. Avatars are often assumed identities with only an oblique relationship to their real-world counterparts. [Variable Media]

AVI - Audio/Video Interleaved file format. [MIC]

Azimuth - Audio/Video A rotation of the tape head away from perpendicular to the direction of tape/head travel. If a head slopes away from the desired angle a loss of signal will occur. [ScreenSound Australia]

Back coat - Optional layer applied to backside of tape substrate layer, useful in reducing tape friction and distortion, as well as dissipating static charge in playback. See image. [BAVC]

Backing - Backing film layer that supports the magnetic layer in a magnetic tape. Polyester Terephthalate (PET) has been the most commonly used tape substrate for analog videotape. Polyeythelene Napthalate (PEN) is commonly used for digital videotapes. Also called base or substrate. [AMIA]

Baking - Tapes [with Sticky-shed] will not playback easily, if at all. If properly identified, these tapes can benefit from exposure to elevated temperatures for several hours, which bakes the binder back onto the base material. This consolidation of binder and base stabilizes the tape system so that it can be played once while the information is copied on to a more stable format. Baking tapes is an extreme measure that irreversibly physically modifies the tape [and should only] be performed by professionals who have experience in dealing with problem tapes. [Vidipax]

Bandwidth - The frequency range of a particular transmission method. In video systems, this value is expressed in MHz, and the better the signal, the greater the bandwidth required. [Projector People]

Bearding - A type of video distortion that appears as black lines extending to the right of bright objects. [BAVC]

Binary - Pertaining to a number system that has just two unique digits... Computers are based on the binary numbering system, which consists of just two unique numbers, 0 and 1. All operations that are possible in the decimal system (addition, subtraction, multiplication, division) are equally possible in the binary system. We use the decimal system in everyday life because it seems more natural (we have ten fingers and ten toes). For the computer, the binary system is more natural because of its electrical nature (charged versus uncharged). [UPF]

Binary number - A number that can be represented using only two numeric symbols, 0 and 1. Binary numbers are used by computers because they can easily be represented and stored by hardware that utilizes switches, magnetic fields, or charge polarities that are normally in one of two states. The on/off, north/south, or positive/negative states can easily represent the 1s and 0s of a binary number, respectively. [AMIA]

Binder - The polymer used to bind magnetic particles together and adhere them to the tape substrate. [BAVC]

Bit - Shorthand for binary digit, which has two optional values "0" or "1." Eight bits means 8 binary digits. There are 256 possible combinations for 8 binary digits and therefore color depth of 8 bits represents 256 (2x2x2x2x2x2x2x2) possible colors. Because each pixel of a video picture contains 3 samples Y', R-Y', B-Y', the possible colors of an 8-bit system would be 16.7 million (256 x 256 x 256). Nowadays archives will be receiving digital material into their collections or will be generating it as part of their preservation program. It is therefore necessary that we understand digital and analog technology. [BAVC]

Bit error rate (BER) - The percentage of bits that have errors in playback. One possible indicator for the deterioration of digital videotape is an increase in the bit error rate prior to error correction. Playback is never perfect and there are many possible causes of error such as noise, dirt and dust, and dropout. In the binary world of digital data a bit is either correct or incorrect. Since it only has two states, the challenge is to correctly identify whether a bit is correct or not. To enable this the data is therefore coded by adding redundant bits. All systems build in redundancy and error correction mechanisms. Information about bit error rates can refer to the bit error rate prior to error correction or the residual errors after error correction. [BAVC]

Bit mapped graphics - The type of graphic that is defined and addressed on a bit-by-bit basis which makes all points on the screen display directly accessible. [Projector People]

Bit rate - The amount of data transported in a given amount of time, usually defined in Mega (Million) bits per second (Mbps). Bit rate is one way to define the amount of compression used on a video signal. [BAVC]

Bitmap - An image made up of a given number of pixels, each with a specific color value, laid out in a grid. Ideal for reproducing photographic representations, because a sufficient quality and quantity of pixels can give the appearance of a continuous tone image. [Getty]

Bitstream - The sequence of 1s and 0s passed among computers and input/output devices, typically containing a text message or audiovisual content. [Variable Media]

Black - A composite color video signal comprised of composite sync, reference burst and a black video signal which is usually at a level of 7.5 IRE (0.05V) above the blanking level. Also refers to fade-to-black between scenes. Also known as Color black and Blackburst. [BAVC]

Blanking level - Also known as pedestal, the level of a video signal, which separates the range that contains the picture information from the range that contains the synchronizing information. [BAVC]

Blocking - The sticking together or adhesion of successive windings in a tape pack. Blocking can result from deterioration of the binder, storage of tape reels at high temperatures, and/or excessive tape pack stresses. See also: Sticky shed. [BAVC]

Blooming - The defocusing of regions of a picture where brightness is excessive. Also refers to adjusting the white levels, on video monitors, to the point of leaving gray and becoming white. [BAVC]

BNC (Bayonet Neill Concelman) - Named after inventors Paul Neill & Carl Concelman. Used with coaxial cables, this connector receives all R, G, B, H-Sync and V-Sync information, and composite video. [Projector People]

Born digital - Creations originally generated in digital form rather than copies or surrogates of analog originals, and which exist entirely in a digital environment. Examples include software, Web pages, hypertext fiction, and digital art. [Getty]

Breakup - Disturbance in the picture or sound signal caused by loss of sync or by videotape damage. [BAVC]

Broadband - High-speed data transmission or a transmission medium in which a wide range or band of frequencies is available to transmit data, allowing more information to be transmitted in a given time frame. As of this writing, broadband is sometimes defined as services that offer bit rates of 1.544 megabits per second (Mbps) and above. May also be referred to as wideband. Digital Subscriber Lines (DSLs) and cable modems allow broadband transmission. See bandwidth [Getty]

Browser - A program that recognizes, interprets, and views Web documents (usually coded in HTML) on the World Wide Web. Netscape and Microsoft Internet Explorer are the most common Web browsers that display graphics as well as texts; others include Mozilla, Opera, and Safari. The same Web page may appear different on different browsers since browsers generally access and interpret codes differently. [Variable Media]

Bumping up - Transferring a program recorded on a lower quality videotape to a higher quality videotape (e.g., from Hi8 to Betacam). Bumping up to a higher format allows footage to be preserved on a more stable tape format and makes it possible to edit in a higher-end editing environment. [BAVC]

Burst (or Color Burst) - The reference for establishing the picture color, burst is seven to nine cycles (NTSC) or ten cycles (PAL) of subcarrier placed near the end of horizontal blanking to serve as the phase (color) reference for the modulated color subcarrier. [BAVC]

Burst vector - In composite video signals, the amplitude and angle of the color reference signal. [BAVC]

Byte - A multi-digit binary number is called a word. A word of 8 binary digits or bits is called a byte. The amount of data that can be moved over time is expressed as MBps (Megabytes per second) or KBps (Kilobytes per second). A kilobyte of memory contains 1024 bytes, one megabyte contains 1024 kilobytes and a gigabyte contains 1024 megabytes. These concepts are essential to understanding issues relating to the storage and format choices of digital materials as well as the terminology surrounding the measurement of errors. [BAVC]

Capstan crease - Wrinkles or creases pressed into the tape by the capstan/pinch roller assembly. See Crease. [BAVC]

Carbon black - An anti-static agent added to tape binder, which also attracts debris to tape. [BAVC]

Carrier - The physical medium on which the video/data is recorded. [AMIA]

Cartridge - A case or container, inserted into a larger piece of equipment, which is easily exchanged, for example a game cartridge in a console, or an ink cartridge in a printer. [EAI]

Catalog - A list of items that records, describes, and indexes the resources of a collection, a library, or a group of libraries. [UPF]

Cataloguing - The process of creating and arranging records that describe materials so as to facilitate identification, search and retrieval, acquisitions, circulation, preservation, rights, evaluation, and collocation. A record generally consists of a description; headings for topics, persons, places, etc.; an identification number; and links to related resources, such as authority records. Differs from a simple listing by the imposition of controlled vocabularies and by mechanisms allowing users to draw relationships between various entities. [Getty]

CAV (Constant Angular Velocity) - The disc speed remains constant while the head-to-disc speed changes. Magnetic discs spin at a Constant Angular Velocity. [AMIA]

CCD - Charged Coupled Device. "The computer chip in video cameras that converts light images into an electronic signal." [BAVC]

Cellulose diacetate. - The type of basefilm used for making audio tapes until the 1960s. It is related in chemical composition to cellulose acetate. [AMIA]

Channels - The separate color components used by various color models. By default, RGB images have three channels: red, green, and blue; CMYK images have four: cyan, magenta, yellow, and black. Extra or 'alpha' channels can be added to describe, for example, levels of transparency, or be used as masks that allow or restrict the output of color. [Getty]

Character generator - Electronic device which produces graphics and characters for creating video titles. [BAVC]

Chat - A text-based interface allowing multiple users to write messages and reply to each other in real time. Examples include ICQ and Instant Messaging. [Variable Media]

Chroma - Video color, or saturation. [BAVC]

Chroma crawl - An artifact of encoded video also known as dot crawl or cross-luminance. Occurs in the video picture around the edges of highly saturated colors as a continuous series of crawling dots and is a result of color information being confused as luminance information by the decoder circuits. [BAVC]

Chroma level - A reference to amount of color saturation; high level chroma that produces pastel, washed out color; low level chroma produces heavy, saturated colors. The absence of chroma would result in black and white. [BAVC]

Chroma noise - A condition in which colors appear to be moving on screen. In color areas of picture, chroma noise is usually most noticeable in highly saturated reds. [BAVC]

Chroma-key - Studio technique combining two video images by replacing a given chroma level from one image with the content of the other content. [Montevideo]

Chrominance - The color part of a signal relating to the hue and saturation, but not to the brightness or luminance of the signal. E.g., black, gray and white have no chrominance, but any colored signal has both chrominance and luminance. U,V; Cr,Cb; I,Q (R-Y, B-Y) represent the chrominance information of a signal. [BAVC]

Cinching - The wrinkling, or folding over, of tape on itself in a loose tape pack. Normally occurs when a loose tape pack is stopped suddenly, causing outer tape layers to slip past inner layers, which in turn causes buckling of tape in the region of the slip. Results in large dropout or higher error rates. [BAVC]

Cleaning - Debris between the head and the surface of a tape will cause errors in playback. However, the term "cleaning" is sometimes used in a general way to refer to more than the removal of debris from the surface of a tape, but to the removal of products of deterioration and other actions of the "cleaning" machines. For example, it may be that one of the important functions of "cleaning" systems is to smooth deformations in the surface of the tape and this function could not correctly be described as cleaning but may be one of the actions being carried out by machines. These cleaning systems have a number of elements - contact with Pellon cloth, a vacuum chamber and a polishing stone. Research could valuably be conducted to establish what the effect of these cleaning systems are, what is being removed, the effect of the different elements and whether modifications could usefully be made. In addition to the systems described on the BAVC DVD Playback: Preserving Analog Video, there are also professionals who have skills and experience to hand clean videotape. [BAVC]

Clipping level - An electronic limit to avoid overdriving the video or audio portion of the television signal [BAVC]

Clone - In digital media, a perfect copy of a given file or files. Unlike traditional media such as analog photography or film, cloned copies are indistinguishable from the original. [Variable Media]

Closed-circuit installation - Installation consisting of one single camera and a monitor that simultaneously displays the recorded images [or live feed].. [Montevideo]

CLV (Constant Linear Velocity) - The disc changes speed as the head moves from the inner track to the outer track. Compact discs (CDs) spin at a Constant Linear Velocity. [AMIA]

CMYK - (Color, Magenta, Yellow, Black) Often referred to as four-color process, CMYK is a subtractive color model, using a mix of cyan, magenta, yellow, and black inks to reproduce a range of colors. CMYK is the most basic color process used in print. [See also RGB]. [Getty]

Code - Instructions written in a language a computer can understand and execute. Examples inlcude Java and JavaScript. [Variable Media]

Codec - A compression/ decompression (sometimes coder/decoder) algorithm or scheme that reduces the volume of bits necessary to store a data object such as an image file (compression) but that allows the reconstruction of the compressed data into a usable format for display, processing, etc. (decompression). There are many different codecs, and they are often used to minimize file transfer time in order to optimize images or data for Web use. [Getty]

Coercivity - The level of demagnetizing force that would need to be applied to a tape or magnetic particle to reduce the remanent magnetization to zero. A demagnetizing field of a level in excess of the coercivity must be applied to a magnetic particle in order to coerce it to change the direction of its magnetization. Coercivity is the property of a tape that indicates its resistance to demagnetization and determines the maximum signal frequency that can be recorded by a tape. Hc is the common abbreviation for coercivity. [AMIA]

Cohesive force - The force that holds a material together. [AMIA]

Color bars - Standard color test signal, displayed as rows or bars of color, used in the alignment of color video equipment. See also: NTSC Color Bars. [BAVC]

Color Resolution - The total number of colors available, expressed in bits per pixel. [Projector People]

Color Temperature - A method of measuring the "whiteness" of a light source. Metal halide lamps produce higher temperatures than halogen or incandescent lights. [Projector People]

Compatible - When different hardware or software can be used together without a major over-haul. [Projector People]

Compilation Tape/Reel - A videotape containing more than one complete work. [IMAP]

Compiled - Said of source code that has passed through an interpreter to render it readable by computers instead of humans. [Variable Media]

Component - A Component TV system has multiple, separate signals and requires two or three cables. [AMIA]

Component video - An unencoded video signal in which luminance (black and white) and chrominance (color) are transmitted as separate components, as such requires greater bandwidth than composite video. Component analog video consists of three primary color signals (RGB) that together convey all necessary picture information. [BAVC]

Composite - Composite is the combination of sync, black/white video and color video signals and uses only one cable. Consumer TV and VCRs are examples of composite video. [AMIA]

Composite video - A mixed encoded signal combining luminance (black and white), chrominance (color), blanking pulses, sync pulses and color burst, that includes horizontal or vertical synchronizing information, using one of the coding standards: NTSC, PAL, SECAM, etc. Chrominance is added as a modulated subcarrier to the luminance signal of approximately 3.58MHz in NTSC and 4.43 MHz in PAL. [BAVC]

Compression - The term used to describe the method of eliminating redundant information in each frame of digital video. Low-level compression of about 2:1 is usually considered lossless. Over about 5:1, compression is lossy. [AMIA]

Conservation plan - A clear articulation of the decision-making process around a proposed course of action, the likely effects of such action and its justification. [BAVC]

Conservation report - A detailed description of the work of art or artifact, its condition, an analysis of the risks to that object and a description of how those risks might be mitigated. If treatment is proposed the report should document each stage of any action taken, the decision making process involved and a description and assessment of the outcome. Reports should be signed and dated. [BAVC]

Consumer Grade - Consumer grade equipment marketed to home users rather than institutions, which are more likely to require professional grade components because of the high demand constant usage places on electronic devices. [EAI]

Contained - In the variable media paradigm, even paintings and sculptures can provoke prickly questions when some aspect of their construction alters or requires an intervention. Such works are "contained" within their materials or a protective framework that encloses or supports the artistic material to be viewed. To account for these alterations in otherwise stable mediums, the variable media questionnaire asks questions such as whether a protective coating is appropriate, whether surface qualities such as brushwork or gloss are essential to the work, or whether an artist-made frame can be replaced. [Variable Media]

Container - The enclosure that contains a reel or cassette of tape [AMIA]

Contrast - The difference between the brightest and darkest parts of the picture. [BAVC]

Contrast ratio - The ratio between white and black. The larger the contrast ratio the greater the ability of a projector to show subtle color details and tolerate extraneous room light. There are two methods used by the projection industry: 1) Full On/Off contrast measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image. 2) ANSI contrast is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing the contrast ratio of projectors make sure you are comparing the same type of contrast. Full On/Off contrast will always be a larger number than ANSI contrast for the same projector. [Projector People]

Control number - A unique number assigned to a specific element of a work. [IMAP]

Control track - A synchronizing signal on the edge of the videotape, which provides a reference for tracking control and tape speed. Control tracks which have heavy dropout or which are improperly recorded may cause tracking errors or picture jumps. [BAVC]

Controlled vocabulary - An established list of terms from which an indexer or cataloguer may select when assigning descriptors or subject headings to a record. See authority, cataloguing. [Getty]

Converting - The process of copying the information on one tape [or other media storage device] to another tape of the same or different format. See also migrate. [AMIA]

Copy - The process of copying the information on one tape to another tape of the same or different format. The term "refreshing" is commonly used by some archivists and librarians to refer to the process of copying information from one tape to a newer tape of the same format (e.g., VHS to VHS). When the information is copied to a different format (e.g., Betamax to VHS), the terms "reformatting" and "converting" have been used. Also called migrate, refresh, transfer. [AMIA]

Copyleft - A strict version of the free software license that requires any modification of the original code to remain free software. For example, programmers who base a product on copylefted code cannot hide the source code from other users. The most common example of a copyleft license is Richard Stallman's GPL (GNU General Public License). [Variable Media]

Crease - A tape deformity, which may cause horizontal or vertical lines in the playback picture. See wrinkle. [BAVC]

Cross-color - A picture defect that appears as spurious rainbow patterns on highly textured objects, such as a striped shirt or a tweed jacket, attributed to the make-up of the NTSC signal, which mixes high luminance and chrominance information in the same composite baseband spectrum. [BAVC]

Crosslinking - A chemical reaction of polymers. Crosslinking will lead to embrittlement when the binder is no longer flexible and the chemical makeup of the binder has changed and tightened. A reaction happens when chemicals within the binder crosslink. Mechanical action of the tape is difficult due to the tightened tape structure. [BAVC]

Crosstalk - An undesired signal interfering with the desired signal, and usually caused by unintentional capacitive (AC) coupling. Can result in several types of picture distortion, mistracking, and/or noisy picture. Also refers to signal interference from one part of videotape to another. [BAVC]

CRT (Cathode-Ray Tube) - The cathode ray tube or CRT, was the display device used in most computer displays, video monitors, televisions, and oscilloscopes until the late 20th century, when plasma screens, LCDs, and other technologies came on the market. A cathode ray tube is a vacuum tube in which a beam of electrons is projected on a phosphor-coated screen to produce a luminous spot at a point on the screen determined by the effect on the electron beam of a variable magnetic field within the tube. [EAI]

CSS (Cascading Style Sheets) - An efficient tool for designing Web sites. By employing CSS, programmers can create style sheets that precisely define the look of Web site. [Variable Media]

Cue points - Time codes or other pointers in an audio or video stream that allow an application such as Director to access audiovisual segments in an different order than their original sequence. [Variable Media]

Curvature error - A change in track shape that results in a bowed or S-shaped track. This becomes a problem if the playback head is not able to follow the track closely enough to capture the information. [BAVC]

DAM - Abbreviation for Digital Asset Management.

Data - Information transmitted as binary code. In the case of component video each pixel is a vector quantity and includes information for all color components Y', R-Y' and B-Y.' High quality standard definition for a moving color picture requires a data rate of 200 million bits per second. [BAVC]

Data Compression - A techique that provides for the transmission or storage, without noticeable information loss, of fewer data bits than were originally used when the data was created. [BAVC]

Database - The most common data-structuring model is 'relational,' where data is organized in related or linked tables that can be accessed or reassembled in many different ways. Object-oriented databases are also common. [Getty]

Database - A collection of information concerning a certain topic organized in a logical fashion for easy access and speedy retrieval. [IMAP]

Decibel (dB) - Unit of measurement for sound levels. [BAVC]

Decoder - A device used to recover the component signals from a composite (encoded) source. Decoders are used in displays and in various processing hardware where component signals are required from a composite source, such as composite chromakeying of color correction equipment, etc. [BAVC]

Degauss - Erase a videotape completely by exposing the tape to a magnetic field. [BAVC]

Demagnetization - A process that erodes audiovisual signals or data encoded onto magnetic tape. This degradation is a natural phenomenon whose speed varies with the type and condition of the tape. [Variable Media]

Derivative file - A file derived or created from another file, rather than created during an original digitization process. Differs from a copy insofar as the derivative file may be altered in some way from the original. [Getty]

Derivative master - A high-quality 'working' image file that is derived from an archival master image file, then subjected to some form of processing, such as color correction. May also be known as a submaster. [Getty]

Desktop - 1. The background image and icons that represent the highest-level folder on a personal computer. 2. Said of applications or activities that operate on a personal computer, as in "desktop publishing". [Variable Media]

Deterioration - The degradation of videotape, most typically with the binder, which is responsible for holding the magnetic particles on the tape and facilitating tape transport. If the binder loses integrity - through softening, embrittlement, loss of cohesiveness, or loss of lubrication - the tape may become unplayable. Sticky tape and sticky shed are commonly used terms to describe the phenomenon associated with deterioration of the magnetic tape binder. [BAVC]

DHTML - A new version of HTML, developed by Netscape and expanded by the W3C (the World Wide Web Consortium). Combines JavaScript's ability to move or rewrite page elements with the CSS method of defining document layout and style to create dynamic Web sites. Unlike closed formats such as Flash, users can directly view the source code of DHTML documents. [Variable Media]

Diacetate - Also referred to as cellulose diacetate. The type of basefilm used for making audio tapes until the 1960s. It is related in chemical composition to cellulose acetate. [AMIA]

Diagonal screen - One corner of a screen to the opposite corner. A 9FT high, 12FT wide, screen has a diagonal of 15FT. If the screen is 12x12, it would still rate 15FT diagonal since that would be the diagonal usable. [Projector People]

Digital - Electronic technology that generates, stores, and transmits data in terms of a limited number of discrete states, most commonly as binary data in which two possible states, positive or nonpositive, are represented by 1 or 0, respectively. Because there are only two possible values, the accuracy of binary digital data at any given point is relatively easy to test, and therefore digital technology facilitates the creation of accurate copies. [Getty]

Digital Asset Management - A system that enables the management of digital objects, such as image files, from ingest to archiving and supports continued retrieval. Off-the-shelf DAM software may offer templates and other devices or strategies to facilitate ingest, metadata capture, and searching. May also be called media asset management (MAM). [Getty]

Digital coaxial - Digital coaxial is the most common type of digital audio connection. A digital coaxial connector appears very similar to a RCA connector, but it transmits digital data instead of analog signals. The electrical signal pulses through a copper wire at the heart of the coaxial cable, which is shielded from interference by an aluminum foil casing. [EAI]

Digital preservation - The specific problems and methods of preserving digital, as opposed to analog, assets because of their vulnerability to format obsolescence and media decay. Various strategies have been developed to respond to this, including documentation, the gathering of preservation metadata, the use of open standards, redundant storage, refreshing, migration, emulation, technology preservation, re-creation, and digital archaeology. [Getty]

Digital projector - A Digital projector is a device that converts image data from a computer or digital video source to a bright image, which is then imaged on a distant wall or screen using a lens system. [EAI]

Digital recording - A recording in which binary numbers represent quantized versions of the voltage signals from the recording microphone or the video camera. On playback, the numbers are read and processed by a digital-to-analog converter to produce an analog output signal. [AMIA]

Digital video - System of recording video images using sequences of binary numbers to encode brightness, colour and timing information necessary to reconstruct the moving image. [ScreenSound Australia]

Digital-to-analog - The process in which a series of discrete binary integers is converted to a continuous analog signal. Sometimes referred to as D-to-A. [AMIA]

Digitization - The process of deriving digital objects from analog originals by converting their sampled values to binary code. Also known as analog-to-digital. [Getty]

Disc - Commonly the term used for optical media, such as Compact Discs, as well as analog sound recordings, such as LPs and transcription discs. [AMIA]

Disk - The term used for magnetic media in non-tape format, such as a computer hard disk or a floppy disk. [AMIA]

Display Device - A display device is a presentation device for visual information. In the case of moving images, a display device typically takes the shape of a monitor or projector. [EAI]

Dissolve - A video transition in which the existing image is partially or totally replaced by superimposing another image. One image fades in as the other fades out. [BAVC]

Distribution amplifier - Amplifier that allows one video or audio signal to be sent to several pieces of equipment simultaneously. [BAVC]

DLP projector (Digital Light Processing) - Digital Light Processing (DLP) is a technology used in projectors and projection televisions. Originally developed by Texas Instruments, with DLP the image is created by microscopic mirrors laid out in a matrix on a semiconductor chip. Each mirror represents one pixel in the projected image. [EAI]

Documentation - Textual information that describes a work of art or image, recording its physical characteristics and placing it in context. May be regarded as one of the most basic preservation strategies for digital files. See cataloguing, digital preservation, metadata. [Getty]

Dot Pitch - The distance between the dots on a CRT display. The closer together the dots are create a higher resolution of a displayed image. [Projector People]

Drop-frame time code - SMPTE time code format that continuously counts 30 frames per second but drops 2 frames from the count every minute except for every tenth minute (drops 108 frames every hour) to maintain synchronization of time code with clock time. This is necessary because the actual frame rate of NTSC video is 29.94 frames per second rather than 30 frames. [BAVC]

Dropout - Momentary signal loss of video or audio during playback on a tape machine, and caused by momentary loss of tape contact with the playback head, tape head clog, flaws in the tape or other features that cause an increase in the head-to-tape spacing. Dropout can also be cause by missing magnetic material. Video dropout generally appears as a white spot or streak on the video monitor. When several video dropouts occur per frame, the TV monitor will appear snowy. The frequent appearance of dropout on playback is an indication that the tape or recorder is contaminated with debris and /or that tape binder is deteriorating. [BAVC]

DTV (Digital TV) - Digital TV refers to the high resolution standard adopted by several countries in 1998-1999. Uses a picture aspect ratio of 16:9 rather than the old standard aspect ratio of 4:3. [AMIA]

Dub - A copy of a video recording, or to make a copy. [BAVC]

Dublin Core - A minimal set of metadata elements that creators or cataloguers can assign to information resources, regardless of the form of those resources, which can then be used for network resource discovery, especially on the World Wide Web. [Getty]

Dubmaster - The copy of a master used for making additional copies. [BAVC]

Duplicated - To say that a work can be duplicated implies that a copy could not be distinguished from the original by an independent observer. This behavior applies to artifacts that can be perfectly cloned, as in digital media, or to artifacts comprising readymade, industrially fabricated, or massproduced components. [Variable Media]

Dynamic range - An audio term which refers to the range between the softest and loudest levels a source can produce without distortion. [Can also refer to the range of brightness and color of an image.] [BAVC]

Echo - A wave which has been reflected at one or more points in the transmission medium. Echoes may be leading or lagging the primary signal, and appear in the picture monitor as reflections or double images commonly known as ghosts. [BAVC]

Edge curl - Usually occurs on the outside one-sixteenth inch of the videotape. If the tape is sufficiently deformed it will not make proper contact with the playback heads. An upper curl (audio edge) crease may affect sound quality. A lower curl (control track) may result in poor picture quality [BAVC]

Edge damage - Physical distortion of the top or bottom edge of the magnetic tape, usually caused by pack problems such as popped strands or stepping. Edge damage effects audio and control track, sometimes preventing playback. [BAVC]

Edit decision list (EDL) - List of edits performed during on-line editing. The EDL can be a handwritten list or computerized set of instructions used to direct the final outline editing assembly of the video programs. [BAVC]

EGA (Enhanced Graphics Array) - EGA is an image which displays 640 pixels by 350 lines with 16 colors from a palette of 64 colors. [Projector People]

EIAJ - Standard tape format for 1/2" VTRs after 1969. [BAVC]

Element - Element is an umbrella term used to refer to an individual videotape or piece of film that is used to create a production. The term can be used to refer to a number of different types of media, including original field tapes, submasters, graphics tapes, audio recordings, etc. [IMAP]

Embrittlement - A tape binder condition resulting from polymers that have chemically meshed & tightened resulting in a less supple tape. [BAVC]

Emulation - A digital preservation strategy that uses current software to simulate original or obsolete computer environments. May either restore full functionality to archival data or provide a simple viewing mechanism. [Getty]

Encapsulation - Encapsulation is a strategy for digital media preservation that groups a digital object with all other entities that are necessary to provide access to that object. In encapsulation, physical or logical structures called "containers" or "wrappers" provide information about the relationships between all data and software application components. Encapsulation aims to overcome the issue of obsolete file formats by including details on how to interpret the original information. [IMAP]

Enhancing - Electronically adjusting the quality and sharpness of a video image. [BAVC]

Erasure - Loss of signal on the tape, resulting from extreme temperatures defined as above 275 F/175 C [or other intentional means]. See Degauss. [BAVC]

Evaluator machine - See Cleaning / Cleaner machine.

Exercising - See Retensioning.

Exhibition format - Tape or disc copies that are used expressly for frequent playback, as opposed to master tapes should only be played as part of the archival process. The criteria for a good exhibition format are different from that of an archival format. For example hard disc, DVD and laser disc are all good exhibition formats for video as they are reliable and because playback is made possible without mechanical deterioration to the media as a result of being played. This is important where a video is on display all day every day. Although in the near future it is likely that we will see uncompressed digital video being streamed from hard discs for display, it is more common that the video is compressed. Such compression would not be acceptable for the master copy but may be a compromise that is acceptable for display. Each media have different advantages and disadvantages, but the important point is to be clear that the criteria for display may be different than for archiving for example the display of a complex video work may require reliable frame-accurate synchronization. [BAVC]

Fade - A dissolve from full video to black video or from full audio to no audio. [BAVC]

Feed - The transmission of a video signal from point to point. [BAVC]

Feedback - A loop caused by audio or video signal being fed back into itself. In video the effect is caused when a camera is directed at its receiving monitor. In audio the effect, manifested as an echo or squeal, is caused when a microphone is aimed at a speaker. [BAVC]

Fiber optic - Fiber optic technology uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of threads, each of which is capable of transmitting messages modulated onto light waves. Advantages over traditional metal lines include greater bandwidth, less susceptibility to interference, and digital transmission of data. [EAI]

Fiber-filled - Fiber-filled envelopes generate dust that is damaging to magnetic tape formats and should not be used to ship videotapes under any circumstances. [EAI]

Field - The building blocks that create cataloging records. Each field stores one particular type of information. [IMAP]

FireWire - FireWire (also known as i.Link or IEEE 1394) is a personal computer and digital video serial bus interface standard that offers high-speed communications and real-time data services. Since 1995, almost all digital camcorders have included a FireWire connection. All Macintosh computers currently produced have built-in FireWire ports, as do all Sony PCs and many PCs intended for home or professional audio/video use. [EAI]

Flagging - A horizontal displacement of the upper portion of a picture. Also called skewing. [BAVC]

Flange - The round disc on either side of a tape reel. [EAI]

Flange pack - A condition where the tape pack is wound up against one of the flanges of the tape reel. [AMIA]

Flash - An animation technology developed by Macromedia Inc. for use on the Web. Compared to other image formats such as GIFs and JPEGs, Flash files download faster and can employ scripting to enable sophistiocated interface design. Unlike open formats such as DHTML, Flash scripts cannot be viewed directly by a user. [Variable Media]

Flat screen - A CRT made more flat than a standard tube by using more than one electron gun. Beneficial to people who require concise reproduction and great detail such as graphic designers. [Projector People]

Flicker - Picture distortion mainly related to vertical syncs and video fields display. Some flicker typically exists due to interlacing and is more apparent in 50HZ systems (PAL). Flicker also shows when static images are displayed on the screen, such as computer generated text transferred to video. Poor digital image treatment, found in low quality system converters (going from PAL to NTSC and vice versa) creates annoying flicker on the screen. There are several electronic methods to eliminate flicker. [BAVC]

Flutter - Very short rapid variations in tape speed which may result in a jumpy or jittery picture. [BAVC]

Focal length - Focal length is the distance between the lens and its focal point. A smaller focal length indicates a wider-angle lens. [Projector People]

Foldover - Tape that has folded over resulting in the oxide surface facing away from the heads. [BAVC]

Format - Refers specifically to tape sizes and qualities, and generally to classes of video equipment. Popular video formats in decreasing order of quality and expense are: Digital Betacam, Betacam SP, Betacam, 3/4" SP, S-VHS, Hi8 and VHS." "[May also refer to] the arrangement of information tracks on [magnetic] tape as prescribed by a standard and the way the signal is processed. The two most common categories of recording formats are longitudinal and helical scan. [BAVC]

Frame - One complete video picture. A frame contains two video fields, scanned at the NTSC rate of 30 frames per second, 525 lines, or the PAL rate of 25 frames per second, 625 lines. [BAVC]

Free software - A software license developed by computer scientist Richard Stallman that permits other users to use, copy, modify, and distribute the source code, with or without a fee. Free software is often developed with an open source model and/or released under a copyleft license. [Variable Media]

Frequency - A measurement of an analog signal's vibration, represented as cycles persecond or Hertz (Hz). [BAVC]

FTP (File Transfer Protocol) - A method for uploading files to and downloading files from Web sites and other computers connected to the Internet. FTP does not allow its users to view file contents, but to simply transfer them efficiently and securely. [Variable Media]

Gain - Gain is a system's mean ratio of signal output to signal input. [EAI]

Gamma correction - A process used with video and computer graphics images to correct brightness and internal micro-contrast within the image, allowing a change of ratio between the brightest red component of an image and the weakest red. [BAVC]

Gamut - The range of voltages allowed from a video signal, or a component of a video signal. Signal voltages outside of the range (i.e., exceediing the gamut) may lead to clipping, crosstalk or other distortions. [BAVC]

GB - A gigabyte (GB or GiB) is a unit of measurement in computers of one thousand million bytes. Because computers work on the binary system, rather than a gigabyte being 103 megabytes (1000 MBs), the term gigabyte can also mean 210 megabytes (1024 MiBs). [EAI]

Generation - Copy of original video program material. The original videotaped material (source footage) is the first generation. A copy of the original is a second generation tape and so on. Generally the edited master tape is a second generation tape. In analog systems, extensive efforts are made to keep generations to a minimum, since each copy or process adds noise and other artifacts resulting in diminished quality with each generation. [BAVC]

Generational loss - Degradation caused by tape duplication. [BAVC]

Genlock - Synchronizing signals between two video sources, which is necessary when overlaying computer graphics on an image from VCR, camera, or videodisc player. [Projector People]

Ghost - A shadowy or weak image in the received picture, offset either to the right or to the left of the primary image, and the result of transmission conditions where secondary signals are created and received earlier or later than the primary signal casued by a reflected RF signal. [BAVC]

Ghosting - A shadow or weak secondary image as seen on a monitor or display which is created by multiple path broadcast transmission errors. [Projector People]

Glitch - A form of low frequency interference, appearing as a narrow horizontal bar moving vertically across the picture. [BAVC]

Global conditionals - Variables in a software program that represent the overall state of the system and can be used to modify it. [Variable Media]

Go-tos - Programming instructions that tell a computer to skip from one line of code to another. Go-tos are a typical hallmark of procedural, as opposed to object-oriented, programming. [Variable Media]

H Sync - AKA Horizontal synchronization. A marker, which indicates to a computer or video signal that it is the beginning of a line. [Projector People]

Hacker - computer programmer of outstanding skills. Hackers are generally granted the term if they are able to create or modify programs, crack codes, defy security system and / or possess a well established computer expertise.

Hard Drive (HD) - A magnetic disk drive used as the main memory of most personal computers. [AMIA]

Hardware - Hardware comprises all of the tangible elements in a computer, as distinguished from the data it contains or operates on and the software that provides instructions for the hardware to accomplish tasks. [EAI]

Hardware-for-hardware - A type of emulation consisting of refabrication or substitution of an artwork's equipment or material. For example, to imitate the physical appearance of the obsolete video monitors in an original video installation by Nam June Paik, reconstructions might custom build cathode-ray tubes or embed flat sreens in old television casings. [Variable Media]

HDTV (High Definition Television) - High definition, wide-screen television broadcasting with digital audio. [Projector People]

Head - Magnetic pickup device in a VTR used to record, erase or reproduce video and audio signals. [BAVC]

Head clogging - The accumulation of debris on one or more heads, usually causing poor picture clarity during playback. Clogging of the playback head with debris causes dropout. [BAVC]

Head switching - ANSI (American National Standards Institute), ASTM (American Society for Testing and Materials), ISO (International Standards Organisation), NISO (National Information Standards Organisation), RLG (Research Libraries Group). [BAVC]

Helical scan - A method of recording video information on a tape resulting in recorded parallel tracks that run diagonally across the tape from one edge to the other. [BAVC]

Hertz (Hz) - A unit used to measure frequency. One hertz equals one cycle per second. [BAVC]

Hi8 - Hi8 is a much improved, highband version of Video8 (8mm video). The peak-white frequency moved from 5.4 to 7.7 MHz. The deviation moved from 1.2 to 2 MHz (making it incompatible with Video8) It produced a horizontal resolution of over 400 lines and had an optional second AFM track for stereo sound. [Vidipax]

Hi-Fi - Short for High Fidelity.

High definition - Television with definition approximately doubled with reference to the conventional TV both vertically and horizontally and with increased picture aspect ratio. A format with a new screen aspect ratio of 16:9 (the current is 4:3) and capable of reproducing twice the resolution in horizontal and vertical dimensions than existing standard definition broadcast systems. [Also referred to as HDTV]. [ScreenSound Australia]

High fidelity - High fidelity refers to a quality standard by which the reproduction of sound or images is very faithful to the original and there exists little or no distortion. [EAI]

High gain screen - A screen that uses one of more methods to collect light and reflect it back to the viewing audience, which will increase the brightness of the image over a white-wall or semi-matte screen. [Projector People]

High resolution - Where resolution is the amount of detail an image holds, higher resolution means more image detail in any media. Image resolution can be measured in pixels, lines, pixels per inch (ppi), and many other ways. [EAI]

Horizontal frequency (kHz) - The total number of horizontal lines scanned per second in a displayed image. [Projector People]

Horizontal resolution - Chrominance and luminance resolution (detail) expressed horizontally across a picture tube. This is usually expressed as a number of black to white transitions or lines that can be differentiated. Limited by bandwidth of the video signal or equipment. [BAVC]

HTML (HyperText Markup Language) - The code used to generate hypertext documents on the World Wide Web through the use of tags and attributes. The "hyper" of the title means that users can jump quickly to other files on the Internet by clicking on linked text or images. [Variable Media]

Hue - (Tint, Phase, Chroma Phase) One of the characteristics that distinguishes one color from another. Hue defines color on the basis of its position on the spectrum, i.e., whether red, blue, green or yellow, etc. Hue is one of the 3 characteristics of television color, along with saturation and luminance. In NTSC and PAL video signals, the hue information at any particular point in the picture is conveyed by the corresponding instantaneous phase of the active video subcarrier. [BAVC]

HVAC - Abbreviation for Heating, Ventilating, and Air-Conditioning systems for storage of media.

Hydrolysis - The chemical process in which scission of a chemical bond occurs via reaction with water. The polyester chemical bonds in tape binder polymers are subject to hydrolysis, producing alcohol and acid end groups. Hydrolysis is a somewhat reversible reaction, meaning that the alcohol and acid groups can react with each other to produce a polyester bond and water as a by-product. In practice, however, a severely degraded tape binder layer will never fully reconstruct back to its original integrity, even when placed in a very low-humidity environment. [AMIA]

Hygroscopic - Said of a material which has a tendency to absorb water. An effect related to changes in moisture content or relative humidity. The hygroscopic expansion coefficient of a tape refers to its change in length as it takes on moisture from the ambient environmental conditions. [AMIA]

Installation - See Video installation.

Installed - For the purpose of variable media guidelines, to say that an artwork must be "installed" implies that its physical installation is more complex than simply hanging it on a nail. Examples of artworks with this behavior are works that scale to fill a given space or make use of unusual placement such as the exterior of a building or a public plaza. For such works, the variable media questionnaire tracks issues of site-specific placement as well as scale, public access, and lighting. [Variable Media]

Interactive - While the word is most commonly applied to electronic media such as computer-driven installations and Web sites, interactivity also describes installations that allow visitors to manipulate or take home components of a physical artwork. The variable media questionnaire tracks such considerations as the type of interface; the method by which visitors modify the work; and the form in which traces of such input are recorded. [Variable Media]

Interchange - The ability to exchange recordings made on machines made by one manufacturer with those recorded on machines made by another manufacturer without affecting the playback of video. [AMIA]

Interlaced - (Short for interlaced scanning) A system of video scanning whereby the odd- and even- numbered lines of a picture are transmitted consecutively as two separate interleaved fields. Also called line interlace. See noninterlaced. [BAVC]

Interlacing - Technique used to reduce flicker caused when the first created video field fades while the next is being written. [Projector People]

Internet art - Art made specifically for viewing or distributing on the Internet. [Variable Media]

Invert image - Many projectors that are ceiling mounted are mounted upside down. Invert image corrects the image digitally so your projected image is not also upside down. [Projector People]

IRE (Institute of Radio Engineers) - Units of measurement dividing the area from the bottom of sync to peak white level into 140 equal units. 140 IRE equals 1V p-p. The range of active video is 100 IRE. [BAVC]

ISO (International Standards Organization) - The organization, founded in 1947 and made up of representatives from national standards bodies, that produces worldwide industrial and commercial standards. [EAI]

Java - A powerful, Web-friendly programming language developed by Sun Microsystems that gives programmers substantial control over the look and function of the interface. [Variable Media]

Jitter - Small and rapid variations in a waveform due to mechanical disturbances, changes in the characteristics of components, supply voltages, imperfect synchronizing signals, circuits, etc. [BAVC]

Jog - Process of moving a videotape forward or backward one frame at a time. [ScreenSound Australia]

JPEG - AKA Joint Photographic Experts Group. An international group, which is working, on a proposed universal standard for the digital compression and decompression of still images used in computer systems. The JPEG idea reduces image size as much as 65:1 and still maintains image integrity by getting rid of subtle color differences the human eye can not see. [Projector People]

KB - A (or kilobyte) unit of information or of computer storage equal to one thousand bytes. [EAI]

Keystone correction - A projectors ability to correct the effects of "pointing up" or "pointing down" at a screen enabling the projector user's audience to view a rectangular image rather than one with a wider top or bottom. [Projector People]

Keystoning - The distortion (usually a wide-top narrow-bottom effect) of a projected image caused by a projector "pointing up" or "pointing down" at its screen. Named after its similarity in shape to the keystone used in constructing an arch. [Projector People]

Laser disc - A form of optical media that, unlike DVD, stores video as a composite analog signal. The laser disc was first introduced by Philips and MCA in 1972, and has been on the market since 1978. Laser discs can be glass or plastic. There are essentially two types of laser disc: those mastered for constant linear velocity (CLV) and those mastered for constant angular velocity (CAV). CAV store approximately 30 minutes of video, can be controlled in a frame-accurate way and can be still framed. CLV discs can store approximately one hour of video but cannot be controlled frame-accurately and cannot be still-framed. Once a popular display format for many artists, the laser disc has now largely been superseded by DVD. Laser discs could not handle saturated areas of color, and would produce artifacts appearing as herring bone patterns. CAV discs did, however, have the advantage of frame-accurate external control. [BAVC]

LCD monitor (Liquid Crystal Display) - A monitor that uses a liquid crystal display. LCD monitors are typically flat screens that need less power than other displays [EAI]

LCD projector (Liquid Crystal Display) - A projector that uses a liquid crystal display. LCD projectors place a small LCD panel, almost always color, in front of a bright lamp, with the input imagery projected through a lens on a flat surface. [EAI]

Leader - The first part of a magnetic tape before the start of the recording. For a VHS tape, this is a clear, non-magnetic material used to determine where to stop the tape during rewind. For other tapes, the leader may be a non-magnetic material spliced on the beginning of the tape (like VHS) or it may be the beginning section of the tape before the program material. This section may be unrecorded, it may contain metadata, or it may have color bars and/or audio tones. [AMIA]

Lenticular - A screen surface that has an embossed geometric shaped pattern that affects view/angle performance and reflection of ambient light. [Projector People]

Linear editing - A form of analog editing in which sequential edits are laid out in a linear fashion from the start to the end of the tape. Precludes inserting footage without re-recording all following edits. In contrast to nonlinear editing. [BAVC]

List server - A program that automatically routes messages via e-mail to all the participants in a discussion group. Examples of List server applications include majordomo and ListServ. [Variable Media]

Long throw lens - A lens designed for projection from the back of a room. Long throw lenses would be used a projection booth in the back of a theater, or from the back of a large classroom. A long throw lens would have to be 50 to 100 FT back to project a 10FT diagonal image. [Projector People]

Longitudinal recording - A recording format in which a slow or fast moving tape is passed by a stationary magnetic record or play (write or read) head. The recorded tracks are parallel to the edge of the tape and run the full length of the tape. [AMIA]

Loop - Video image edited in such a way that it has no (clearly defined) beginning or end. [Montevideo]

Lossless compression - Coding essentially expands to provide identical data, bit for bit, with the original source data, although the processing does introduce the possibility of errors. The compression factor of such a system is usually around 2:1. Digital Betacam is a format that employs "lossless" intra-coded compression. [BAVC]

Lossy compression - Coding does not expand to produce identical data to the source material and differences are detectable. MPEG 2 is an example of a lossy inter-coded compression standard. MPEG-2 is the compression system used for DVD. [BAVC]

LTC (Longitudinal Time Code) - Another expression for the SMPTE time code signal recorded onto the third audio track of a videocasstte tape. [BAVC]

Lubricant - A component added to the magnetic layer of a tape to decrease the friction which occurs between the head and the tape during playback. [AMIA]

Lubricant loss - The loss of a component added to the magnetic layer of a tape to decrease the friction between the head and the tape. [BAVC]

Lumen - 1. Unit of light output. 2. The measure of luminous flux (the rate at which light pulses are emitted or received). For instance, one candela of light covering a square foot of surface. [ScreenSound Australia]

Luminance - The portion of the video signal which contains the black and white information. Luminance indicates the amount of light intensity in a picture which is perceived by the eye as brightness. The color video picture information contains two components: luminance (brightness and contrast) and chrominance (hue and saturation). [BAVC]

Mac (Macintosh) - A popular operating system developed in the 1980s by Apple Computers, noted for its graphic interface and ease of use. [Variable Media]

Machine code, Machine language - The 1s and 0s that a software program sends to a computer's processor to run the program. Whether compiled or not, all source code eventually becomes machine code when it is running. [Variable Media]

Magnetic media - Tape and discs that store information on a magnetized surface such as videotape, audiotape or computer floppy discs. [BAVC]

Magnetic particles - The materials incorporated in the binder to form the magnetic layer on a magnetic tape. Iron oxide, chromium dioxide, barium ferrite, and metal particulate are various examples of magnetic pigment used in commercial tapes. The term 'pigment' is a carry-over of terminology from paint and coating technology - the magnetic coating on a tape is analogous to a coat of paint in which the magnetic particle is the paint pigment. [AMIA]

Magnetic remanence - The ability of the pigment to retain a magnetic field [BAVC]

Magnetic tape - A plastic, paper, or metal tape that is coated or impregnated with magnetizable iron oxide particles on which information is stored as a pattern of polarized spots." (Screensound): "With few exceptions, magnetic tape consists of a base film coated with magnetic particles held in a binder. The magnetic particles are usually of a circular shape and approach single domain size. [UPF]

Main memory - Also known as RAM (Random Access Memory), information stored in the active virtual memory of a running computer. Information in RAM is lost when the computer is turned off, unless it has been saved to disk first. [Variable Media]

MARC (MAchine Readable Cataloging) - The standard system for computerizing cataloging records. In US, also called USMARC, and systems may vary internationally, e.g., DenMARC. [BAVC]

Master - The earliest generation of a finished tape that should also be of the best quality. Masters should not be used as exhibition tapes, i.e., not for repeated playback. See also dubmaster. [BAVC]

MB - A megabyte is a unit of information or computer storage equal to one million bytes. [EAI]

Metadata - Commonly defined as 'structured data about data,' or data captured in specific categories or elements. Metadata can include data associated with either an information system or a data object or set of objects for purposes of description, administration, preservation, the documentation of legal requirements, technical functionality, use and usage, and so forth. [Getty]

Metal Halide Lamp - The type of lamp used in most high-end portable projectors. These lamps output a very "hot" temperature light, similar to lamps used in streetlights. Metal Halide whites are super white (with a hint of blue) and make Halogen lamp white appear very yellowish by comparison. [Projector People]

Metal-evaporated tape - These tapes require no binder polymer, as the entire magnetic layer comprises a single, homogeneous metal alloy layer that is evaporated onto the substrate. Their chemical stabilities are similar to those of metal-particle tapes. However, because the magnetic coating on a metal-evaporated tape is much thinner than the corresponding layer on a metal-particle tape, they are also generally not as durable. Repeated play or freeze-frame video applications present problems with wear. [See Magnetic particles]. [Vidipax]

Metal-particle tape - Metal-particle and chromium-dioxide pigments provide a higher tape signal output and permit higher recording frequencies than do iron-oxide pigments. They are not, however, as stable as iron-oxide pigments. A decrease in signal output of two decibels may be observed over the lifetime of metal-particle and chromium dioxide-based tapes. Even with these losses, the output signal will still be better than a comparable iron oxide-based tape... Metal particulate is used in high-grade audio and low-to high-grade video tape. Metal particles are also used in most digital audio and video tape formulations. [See Magnetic particles]. [Vidipax]

Micron - A unit of measure for the thickness of magnetic tape. Symbol is µm. [AMIA]

Migrate - Digital preservation strategy that involves transferring data from a format or standard that is in danger of becoming obsolete to a current format or standard." Other interchangeable (if not precisely synonymous) terms include: converting, copying, refreshing, reformatting, transferring. [Getty]

MiniDV - See DV.

Mirroring - Duplicating a file, typically a Web site, in another location so as to distribute access to or safeguard the original work. [Variable Media]

Mistracking - The phenomenon that occurs when the path followed by the read head of the recorder does not correspond to the location of the recorded track on the magnetic tape. Mistracking can occur both lon