F

f/Number or f/Stop - focal length/aperture

Facsimile - Reproduction of hard copy paper) documents electronically transmitted over the telephone lines. Also called fax

Fade - Varying the strength of a picture—either from black to full strength fade in~ or from full strength to black (fade out)

Far-Infrared Radiation.  Radiation with a wavelength exceeding 4 microns. Surface temperature increases when this radiation is applied to an object.

FCC-   Federal Communications Commission. The governmental agency which makes all policy and has control over the use of air waves for broadcasting

Feedback - The regeneration of sound caused by a system’s microphonic pickup of output from its own speakers causing a ringing sound or squeal

Fiber Optic - A transmission designed to transmit signals in the form of pulses of light. Fiber optic cable is noted for its properties of electrical isolation and resistance to electrostatic and electromagnetic interference

Field - One half of a standard television frame, containing every other line of information. Each standard video image contains 2 fields interlaced. In the NTSC video system, a field contains 262.5 lines, a frame contains 525 lines. There are 2 fields per frame in standard video. Some ATV systems are attempting to include all scanning lines in a single field so that 2 fields will not need interlacing to provide a single frame (image)

Field Frequency - The number of fields per second is the field frequency; NTSC field frequency is 60 per second; PAL and SECAM frequencies are 50

File-  A collection of organized or related data. When stored on a disk, the file is normally given a name (See also FILENAME) which corresponds to an entry in the disk’s directory

Filename - A name given to a particular file, usually on a disk. In MS-DOS, a filename can be up to 8 characters long, with a 3-character extension. Filenames are stored in the disk directory, and can be changed if desired

Film Chain-    A system of fixed video camera(s) and appropriate projectors used to transmit projected materials, system. Ordinarily includes projectors, multiplexer and video camera on a rigid frame

Filmstrip-   A series of still pictures on a strip of film usually single-frame 35mm, but sometimes 110, SuperB or 16mm formats). The filmstrip may be silent or provided with an accompanying sound program tape or record). Filmstrips may be advanced manually as desired or in response to an audible beep in the audio source, or, if so equipped, automatically by a cue tone on the record/tape

Filmstrip Projector - 4 device containing a lens system which focuses an image from a filmstrip onto a viewing screen. Filmstrip projectors can be designed for either front or rear projection and may be used for either large or small audiences. Contrast with FILMSTRIP VIEWER

Filmstrip Viewer - A unit for direct viewing of a back lighted image on the filmstrip with the aid of magnification. Viewers are most suitable for individual use because of the narrow viewing angle. Contrast with FILMSTRIP PROJECTOR

First Surface Mirror - See MIRRORS

Flat Screen-  A flat reflecting surface with 180 viewing angles and gains approximately equal to 1.

Floating Point-  Refers to the position of the decimal point in a type of arithmetic commonly used for high precision scientific calculations

Floppy Disk - A removable, flexible, magnetic storage medium used to store data. The most common floppy disk sizes are 8” and 5.25”, and 3.5

Floppy-  Diskette, plastic cased magnetic storage disk

FLOPS-  One floating point Operation Per Second; a measure of peak vector processing speed in supercomputers

Fluid Head Tripod-  A tripod whose camera mount consists of two metal plates separated by a layer of fluid movement is very smooth

Flutter-   Rapid change in frequency of an audio or video signal due to variations in tape or disc speed. A WOW is usually considered a lower frequency speed variation

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Flying Erase Head -   A combination record/erase head found on video camcorders and recorders which provides cleaner edits

FM (Frequency Modulation)-   A method by which sound frequencies are carried in radio transmission; more noise free and generally with a broader frequency range than AM (Amplitude Modulation) transmissions. Desirable for high fidelity applications

Focal Length (FL)-  The distance between a focal point of a lens or mirror of projection equipment and the corresponding principle plane. Shorter focal length means larger image size on the screen for given projection distance

Focus - The picture adjustment control that adjusts the CRT electron beams to control the sharpness of the display. May increase the amount of picture noise

Focus (Automatic) - A device on slide projectors whereby after focusing the first image, remaining similarly mounted slides are automatically focused

Font - Specific type and size of alphabet characters

Footcandle - The amount of light reflected by a surface one foot from a lighted candle. Metric equivalent is LUX

Footlambert - One LUMEN or one footcandle of light over a one square foot surface

Format - A pattern, usually tracks and sectors, which allows a computer to read and write data on media, such as magnetic or optical storage disks

FORTRAN. Stands for “Formula Translation” a programming language developed in the late 1950s for solving scientific and mathematical problems

FPS (also FR/S)-  Frames per second, The motion picture industry commonly uses “fps” to mean frames per second

Frame - In video, a single image on a display created by storing a continuous sequence of scan lines. In film, action and movement are depicted by a series of still frames shown very quickly

Frame Animation - Animation procedure in which a screen image is drawn by the computer, then recorded on a frame of film or videotape. Animation sequences of this type can take a long time to create, but are usually of very high quality

Frames Per Second. Frequency with which video frames appear on a monitor. Broadcast-quality video generally consists of 30 frames per second. Full-motion videoconferencing typically offers video in the range of 10-15 frames per second. At very low bandwidths, such as 56 on 12 kilobits per second, the frame rate may be lower.

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Freeze Frame - The event itself, or the device used to capture a single field or a full frame from a sequence in full motion. Also used to describe transmission of a single frame of video depicting a still or frozen graphic image.

Frequency- The number of times a signal repeats in one second, measured in Hertz (cycles per second). The frequency equals 1/period

Frequency Division Multiplex - A form of programming multi-image devices based on a variety of audio tones used in combinations to carry the commands. Compare with TIME DIVISION MULTIPLEX

Frequency Response - The frequency range in audio and video systems over which signals are reproduced within a stated amplitude range. Generally expressed in dB versus Hz: example 100-5000Hz * 5dB

Fresnel - A flat glass or acrylic lens in which the curvature of a normal lens surface is collapsed into small steps in an almost flat plane, resulting in concentric circle forms impressed or engraved on the lens surface. Because of lower cost, less weight and compactness, it is often used for the condenser lens in overhead projectors and in studio spot and floor lights

Front end - Initial filter stage of a receiver

Front Screen Projection - An image projected on the audience side of a light-reflecting screen

F-Stop - In lenses with adjustable irises, the maximum iris opening is expressed as a ratio (focal length of the lens)/(maximum diameter of aperture)

FTP (File Transfer Protocol) - A method of moving files between two Internet sites. FTP is a special way to log in to another Internet site for the purpose of retrieving and/or sending files. There are many Internet sites that have established publicly accessible repositories of material that can be obtained using FTP by logging on using the account name “anonymous,’ thus these sites are called anonymous ftp servers’

ft/s - Feet per second

Full-Duplex - Two-way communication as opposed to simplex or half-duplex, or one-way communication. In a two-site duplex videoconference, both parties can send and receive video, audio and data simultaneously.

Full-Motion - In compressed video, picture quality that is generally acceptable to users although not of broadcast quality. Typically full-motion video provides 10-15 f/p sec.

Function Key - A computer key that can be programmed for a specific purpose, often unique to the application which uses it. On the IBM PC, the function keys are on the left side of the keyboard labored “Fl” through F10”. Also known as SOFT KEYS

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G

Gaffer - Chief set electrician

Gain or Screen Gain - The ability of a screen to amplify incident light. A flat matte white wall has a gain of approximately 1. Screens with gain less than 1 attenuate incident light, screens with gain more than 1 amplify incident light. For example: An image reflecting off a 10 gain screen appears 10 times brighter than it would if reflected off a matte white wall. Curved screens usually have larger gain than flat screens. Dual-purpose rear/front screens often have gains of about 0.5 in each direction

Gain - The amplification of a unit or system. May be expressed in dB for electronic equipment or a factor times) for screens

Gamma Correction - This enhances contrast for brighter, lifelike images.

Genlock - A device which locks the frequency of its internal sync generator to an external source

Geometry - The ability of a projector to accurately reproduce the border around a rectangular image

GHz - Gigahertz; 1 billion cycles per second. A unit of frequency.

Glass Beaded - See SCREEN SURFACES

Glitch - An intermittent error in a circuit

Global - Refers to statements and changes which affect an entire program. For instance, if there are 100 pages of information being processed, and a global change is made, it will affect all 100 pages, not just the current page

Graphics Adaptor - provides color display capabilities of text and graphics images- It has an output for an RGB (TTL) monitor, as well as a standard composite video output

Graphics Display - A high-performance display terminal designed for specialized applications such as business graphics and technical publishing

Graphics Environment - An extension of a computer operating system that allows applications programs to operate in a graphics based environment. Such an environment often uses icons, drop-down menus, and integrated text and graphics

Graphics Tablet - A notebook sized writing surface which uses an “electronic pen” or “stylus” for input. It converts the position of the stylus to a set of  X and Y coordinates which are then sent to the computer

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Gray Scale - A series of tones which range from true black to true white, usually expressed in 10 steps.

Ground - A conducting connection by which an electric circuit or equipment is connected to the earth to establish and maintain a reference voltage level. The voltage reference point in a circuit

H

H. 221 The ITU-T standard relating to communications protocol for videoconferencing.

H.261 - The ITU-T Px64standard relating to the video compression algorithm.

H.320 - A group of standards, (for Narrow Band Visual Telephone Systems and Terminal Equipment), established by the CCITT (now TSS) to facilitate the deployment of videoconferencing on a worldwide basis. Specific standards included in this overall standard: H.261 (motion video compression), G.711/722/728 (audio compression), H.231/243 (multipoint conferencing), H,242 (communication between terminals}, H.233 (encryption) and others.

Half-Duplex Audio - Audio that permits only one site to speak at a time.

Hard Disk - A high-density magnetic storage device capable of storing a large amount of data. Hard disk systems are usually built into the computer and the disks are not usually removable

Hardware - The electronic and mechanical components of a computer system

Hash - A term for audible radio interference

HD - High Definition; often meaning -IDEP and HDTV

HDEP - High Definition Electronic Production

HDTV - High Definition Television, a term used to describe advanced production and delivery systems

Head - A small electromagnet which places magnetic signals onto a video or audiotape as it moves by; also reads those signals off a tape. Heads must be positioned or aligned correctly so they follow the correct path across the tape. Heads out of alignment will not record or play well

Head Demagnetizer (Degasser) - A device which provides an alternating magnetic field used during routine maintenance to remove the residual magnetism from recording or playback heads

Headend - The electronic equipment located at the start of a cable television system

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Headphone - A device consisting of one or two electro­acoustic receivers attached to a headband for private listening to audio sources; sometimes called Earphone. Compare with HEADSET

Headset - A headphone with a built-in microphone usually mounted on an adjustable boom. It is audio active, meaning the wearer can both listen and respond

Heat Filter (FR Filter) - A stage in the condenser lens system to filter out infrared (IR) waves in order to reduce heat on film

Helical Scan Video Tape Recording - A type of video recording in which the video heads and the tape meet at such an angle that the resulting pattern on the tape is a long, diagonal series of tracks from the video heads, each diagonal stripe containing the full information for 1 field of video picture. Named after the helical path the tape describes between supply and take-up reels. Also called slant track

Hertz (Hz) - The frequency of an alternating signal. Formerly called cycles per second or CPS

Hertz System. 50 (50Hz) - System for automatically advancing visual materials, usually filmstrips, by a 50Hz signal on the audio program, usually a compact cassette, according to ANSI Standard PH74. In playback the audio signal is divided by filters allowing the program material to pass through in a normal manner and the 50Hz cue tone to advance the visual or perform some other function. Ordinarily prepared by commercial producers rather than locally

Hertz System. 1000 (also 1kHz system) - System for automatically advancing visual materials by a 1000Hz signal on a separate tape track, usually in a compact cassette according to ANSI Standard PH7.4. The cassette can be used in only one direction. Equipment is available for local recording of cue tones

Heterodyne - To combine signals of various frequency in a manner that produces additional signals at frequencies which are sums and differences of the original frequencies

Hexadecimal - Numbering system based on the power of 16. A convenient numbering system when working with binary digits because its base value is a power of 2. The 16 numbers are represented by the digits 0 through 9 and the letters A through F

HGA - Hercules Graphics Adaptor

Hi8 - A sharper version of 8mm, it gives about 400 lines of resolution.

High Fidelity - Accurate and faithful reproduction of the original; absence of distortion

High Resolution - Camera or monitor with a great number of scanning lines (1000-2000) which produces a very sharp, detailed image

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Holography - A technique for recording and reconstructing the amplitude and phase distributions of a wave disturbance, holography is used in three-dimensional optical image formation and with acoustical and radio waves.

Homing (also Resync) - A projector feature which causes the projector to automatically return to its starting point

Host Computer - Typically a mainframe or minicomputer which supports a network of display terminals

HTML (Hypertext Markup Language) - The coding language used to create Hypertext documents for use on the World Wide Web. In HTML you can specify that a block of text, or a word, is “linked” to another file on the Internet. HTML files are meant to be viewed using a World Wide Web Client Program, such as Mosaic

Hub- Central part of a reel on which tape or film is wound

Hue - Color; value red, green, blue, yellow) rather than intensity or brightness

Hum - Audible disturbance caused by the power supply

Hypercardioid - A unidirectional microphone with tighter front pickup 105% than a supercardioid, but with more rear pickup. Angle of best rejection is about 1 ~ from the front of the microphone

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