Resource Center: How to Speak A/V
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Entries starting with: fade: A video transition technique in which a scene gradually recedes into black (fade out) or emerges out of black (fade in). Some camcorders allow fades in and out of white or some other color; see dissolve. feedback: In electronics, negative feedback is the return of a small portion of the output signal to the input, in reversed polarity, usually to reduce distortion. Positive feedback is used in sine-wave oscillators and other test-tone generators. ferrofluid: A ferromagnetic liquid (magnetic particles suspended in oil) used in some speaker drivers, especially tweeters, to conduct heat away from the voice coil and improve damping and power handling. fiber-optic: A transmission medium in which signals are carried through a special plastic- or glass-fiber cable in the form of light; the primary benefit is immunity to electrical noise. See Toslink, ST. field: One-half of the scan lines of an interlaced frame; see frame, interlaced. field-effect transistor (FET): A semiconductor amplifying device that behaves more like a triode vacuum tube than like a bipolar transistor. 50-dB quieting sensitivity: A tuner specification that indicates the RF signal strength (in microvolts or dBf) required for an incoming FM signal to produce a background noise level 50 dB below the audio output at full modulation; lower figures are better. filter: A circuit — like the crossovers found in subwoofers and speakers — that boosts, attenuates, or removes selected frequencies from audio signals. firewall: A system for preventing network access by unauthorized users. FireWire: An industry-group brand name for the high-speed, high-capacity digital data-transmission standard that’s also known as i.Link and DTVLink; see IEEE 1394. first-surface mirror: A mirror whose reflective coating is on the top, the first surface the light hits, unlike the typical “second surface” bathroom mirror; used in rear-projection TVs to reflect the image onto the back of the screen. 5.1-channel: The conventional designation for a medium or system that carries six channels of sound information: front left/center/right, surround left/right, and a restricted-bandwidth (hence the “.1”) LFE channel. fixed-pixel display: Any display technology that utilizes separately activated pixels of constant size. Of the major TV display technologies, only CRT is not fixed-pixel. flash memory: A type of nonvolatile random-access memory; flash memory can be embedded in circuitry or placed on a removable card. flat: Applied to frequency response, a condition in which all input frequencies emerge from the device or medium with the same relative levels as when they entered. Also a setting, as of an equalizer or tone control, that results in a flat frequency response. flying erase head: An erase head mounted on a camcorder or VCR’s rotating head drum that can selectively erase the video information only, without disturbing the tape’s audio, timing, and synchronization signals; allows accurate, glitch- and noise-free video editing. focal length: The distance between the optical center of a lens to its focus point. footlambert (ftL): A measure of the brightness of TVs; 1 ftL is the luminance (brightness) of a surface emitting or reflecting light at a rate of 1 lumen per square foot. 4:3, 4x3: The squarish shape of a traditional, nonwidescreen TV; see aspect ratio. frame: A complete, individual picture on a motion-picture film or contained in a video signal. frame rate: The rate at which frames are displayed. In typical modern movies the frame rate is 24 per second; in color NTSC video it’s 30 per second. frequency: Rate of vibration or oscillation, measured in cycles per second, or hertz (Hz). The audio spectrum is generally taken to be 20 to 20,000 Hz (20 Hz to 20 kHz), which encompasses all the frequencies humans can hear. In radio, frequency refers to the carrier signal of the station, such as 88.1 MHz for an FM station or 770 kHz for an AM station. frequency modulation (FM): A technique in which the frequency of a high-frequency carrier is varied according to the level of a much lower-frequency signal. Commonly used to impress an audio signal onto a radio-frequency (RF) carrier, as in FM radio. frequency response: The range of frequencies (or bandwidth), expressed in hertz (Hz), that a component can handle, within specified limits of level error, expressed in decibels (dB); for example, “35 Hz to 18.5 kHz ±3 dB.” frequency synthesis: The process by which the various reference frequencies required by a tuner are derived by division of a single reference frequency, usually obtained from a stable quartz oscillator (see phase-locked loop). Frequency synthesis allows such tuner features as digital frequency readouts and station presets along with improved audio performance. front end: The first stage of a radio or TV tuner, responsible for selecting and amplifying the desired signal. front projector: A type of video display in which the projector elements are housed in a separate unit, not connected to the screen and mounted in front of it, much like a movie projector; front projectors are often mounted on the ceiling. f-stop (f/): A number describing the relative size of a lens aperture in a camera, derived from the focal length divided by the aperture diameter and normally rated in standardized discrete steps (1, 1.4, 2.0, 2.8, 4.0, 5.6, 8, and so on). Moving from one f-stop to the next lower stop theoretically doubles the amount of light falling on an image sensor. Commonly referred to as the “speed” of a lens, a misnomer. Abbreviations |
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