A circuit that converts a signal from analog to digital form; the opposite of a D/A converter.
Automatic Gain Control. A circuit that automatically adjusts the input gain of a device in order to provide a safe and consistent signal level. AGC's can be handy features, but professional applications often require manual gain control for optimum results.
Amplitude Modulation. A method of radio transmission which sends information as variations of the amplitude of a carrier wave.
The amount of electrical current transferred from one component to another.
A device which increases signal amplitude.
To increase amplitude.
The strength or power of a wave signal. The "height" of a wave when viewed as a standard x vs y graph.
Information stored or transmitted as a continuously variable signal (as opposed to digital, in which the analogue signal is represented as a series of discreet values). Analogue is often technically the more accurate representation of the original signal, but digital systems have numerous advantages which have tended to make them more popular (a classic example is vinyl records versus CDs).
A device which radiates and/or receives electromagnetic waves.
Literally means "opening". The camera iris; the opening which lets light through the lens. By adjusting the size of the aperture, the amount of incoming light is controlled. The aperture size is measured in f-stops.
The ratio of width to height of an image. Can be expressed as a number, or a relationship between two numbers. For example, the standard television screen ratio is 4:3 (4 units wide by 3 units high) or 1.33 (the width is 1.33 times the height). The new "wide screen" or HDTV television ratio is 16:9 (1.78), and many new video cameras have the option to record using this format. Theatrical film aspect ratios vary, but the most common is 18.5:10 (1.85).
Sound. Specifically, the range of frequencies which are perceptible by the human ear.
Functions which are performed by equipment with little or no input from the operator. Auto-functions can be very useful, but tend to have serious limitations. As a general rule, it is desirable to be able to operate audio-visual equipment manually.
On audio mixers, a bus which has an independent feed from each individual channel. Each channel has a pot to adjust the level being sent to the auxiliary master output, which in turn has a pot to adjust the overall level at the output bus. The auxiliary channel may be a simple output (to feed a device such as a tape machine or monitor), or it may be a "loop". An auxiliary loop sends a signal from the auxiliary output bus to a signal processing device such as a reverb generator, then brings the output of that device into an "auxiliary return" bus (thus creating a loop from the desk to the device, back to the desk). This return bus will have a level control pot, which is used to mix the incoming signal into the mixer's master output bus.
"Audio Video Interleaved". A common digital video format, in which the audio is interleaved as "packets", into the video frames.
A light which is positioned behind the subject. It's primary purpose is to make the subject stand out from the background by highlighting the subject's outline.
The focus between the lens and the camera. Adjusted by a ring at the rear of the lens (the closest ring to the camera body). If the camera appears focused when zoomed in, but becomes out of focus when zoomed wide, the back focus needs adjusting.
An audio signal which consists of two "hot" signals plus the shield. The hot signals are 180 degrees out of phase with each other as they travel along the balanced cable. They are placed back in phase when entering an audio device - this has the effect of placing any unwanted interference out of phase, thus eliminating it.
A circuit which filters out all but a certain range of frequencies, ie. it allows a certain band of frequencies to pass.
A range of frequencies.
Metal projections attached to the front of a light, which can be positioned in various ways to control the dispersal of the light.
Unit of signal speed - the number of signal "bits" per second.
On a film set, the assistant to the Gaffer and Key Grip.
(1) A group of video formats developed by Sony Corporation. Beta, Beta SP, Digital Beta and other variations are all professional television formats. Betamax is a failed consumer version, losing to VHS in the 1980's.
(2) A pre-release version of computer software. Often distributed widely without charge, in order to obtain feedback, identify bugs, and attract customers.
The "base two number system" which computers use to represent data. It uses only two digits: 0 and 1. Binary code represents information as a series of binary digits (bits). In the table below, binary numbers are shown with their decimal equivalents. Binary = 0 1 10 11 100 101 110 111 1000 1001 1010 Decimal = 0 1 2 3 4 5 6 7 8 9 10
Binary digit. One piece of binary (digital) information. A description of one of two possible states, eg 0 or 1; off or on.
A series of digital image formats, which record colour information for each individual pixel. As a result, the quality is very high, as is the size of the file.
Square/rectangular metal part which screws to the bottom of the camera plate, and allows the plate to attach to the head. The biscuit comes as part of the head's package, whereas the plate comes with the camera. The biscuit is the "interface" between the two, and is designed to attach to any plate, and fit into a corresponding slot on the head. When the head's quick-release mechanism is activated, the biscuit, plate and camera are all released as one.
A camera function which gives a reference to true black. When auto-black balance is activated (by a switch, positioned with the white balance switch), the iris is automatically shut, and the camera adjusts itself to absolute black.
A composite video signal with no luminance information, but containing everything else present in a normal composite video signal.
A solid coloured horizontal bar across the bottom of a colour bar test pattern. The most commonly used bucket colour in PAL patterns is red, referred to as a "bucket of blood".
Pathway which a signal passes along. For example, the main output of an audio mixer is referred to as the master bus.
A group of eight binary (digital) bits
A system of television program delivery via cable networks.
A single unit consisting of a video camera and recording unit.
The components which deal with light rays, before they are converted into electrical signals (ie. the lens, etc).
A measurement of light, generally that which is output from an electric lamp.
see Charged Coupled Device.
Camera Control Unit.
Compact Disc. Optical storage device, capable of storing around 600-700KB of data.
(1) On audio mixers, the pathway along which each individual input travels before being mixed into the next stage (usually a sub-group or the master bus). Each channel will typically have an input socket where the source is physically plugged in, followed by a sequence of amplifiers / attenuators, equalisers, auxiliary channels, monitoring and other controls, and finally a slider to adjust the output level of the channel.
Charged Coupled Device
The image sensing device of video and television cameras -- the component which converts light from the lens into an electrical signal. Made up of pixels - the more pixels, the higher the resolution. CCDs are commonly referred to simply as "chips". They replaced previous tube technology in the 1980's. Larger CCDs can naturally accommodate more pixels, and therefore have higher resolutions. Common sizes are 1/3" (pro-sumer level), 1/2" and 2/3" (professional level). Consumer cameras generally have a single CCD which interprets all colours, whereas professional cameras have three CCDs -- one for each primary colour.
Chroma, or colour. In composite video signals, the chrominance component is separated from the luminance component, and is carried on a sub-carrier wave.
A video camera function which allows the camera to alter it's scan rate to match that of a computer monitor. This reduces or eliminates the flicker effect of recording computer monitors.
A television test pattern, displaying vertical coloured stripes (bars). Used to calibrate vision equipment. There are numerous variations for different applications.
A standard of measuring the characteristics of light, measured in degrees Kelvin.
(1) A method of reducing the size of a digital file, whilst retaining acceptable quality. This may be desirable in order to save memory space or to speed up access time. In the case of digital video, large files must be processed very quickly, and compression is still essential for playback on consumer-level computers. Professional digital systems can work with uncompressed video. There are many compression techniques in common use, and digital video often uses various combinations of techniques. compression can be divided into two types: "lossless" and "lossy". As the names imply, lossless techniques retain all of the original information in a more efficient form, whereas lossy techniques discard or approximate some information. With lossy compression, there is an art to finding a compromise between acceptable quality loss, and file size reduction.
(2) Audio compression is a method of "evening out" the dynamic range of a signal. Compression is very useful when a signal is prone to occasional peaks, such as a vocalist who lets out the odd unexpected scream. The compressor will not affect the dynamic range until a certain user-definable level is reached (the "threshold") - at which point the level will be reduced according to a pre-determined ratio. For example, you could set the compressor to a threshold of 0db, and a compression ratio of 3:1. In this case, all signals below 0db will be unaffected, and all signals above 0db will be reduced by 3db to 1 (ie. for every 1db input over 0db, 1/3db will be output). Other controls include the attack and decay time, as well as input and output levels.
Camera movement across, and parallel to, the scene.
An electrical network which divides an incoming audio signal into discreet ranges of frequencies, and outputs these ranges separately.
Cathode Ray Tube.
(1) An instantaneous transition from one shot to the next.
(2) A location director's instruction, calling for the camera and audio operators to cease recording and all action to halt
D Series Tape Formats
A series of broadcast digital formats, designated D1, D2, etc. Dx is basically a replacement for 1-inch formats. D2 and D3 combine chrominance and luminance information, whereas D1 and D5 store them separately (and are therefore higher quality).
Digital Audio Tape.
Direct Current. The electrical current output by batteries, etc.
Logarithmic measurement of signal strength. 1/10 of a Bel.
Depth of Field
The zone between the nearest and furthest points at which the camera can obtain a sharp focus.
Method of amplifying a signal, in which the output signal is a function of the difference between two input signals.
A signal which consists of a series of discreet values, as opposed to an analogue signal, which is made up of a continuous information stream.
Professional digital tape format, introduced by JVC in the mid-1990's.
A transition in which one shot dissolves into the next.
Any apparatus upon which a camera can be mounted, which can be moved around smoothly.
Toward the camera.
Loss of part of a recorded video or audio signal, showing up as glitches on playback. Can be caused by damaged record heads, dirty tapes or heads, etc.
Rehearsal without recording or transmitting etc.
Professional digital tape format from Panasonic, introduced in the mid-1990's.
(Digital Video Disc or Digital Versatile Disc). An optical disc format which provides sufficient storage space and access speeds to playback entire movies.
Loudspeaker which uses conventional cone and dome drive elements.
A moving coil microphone, which doesn't require power.
An unwanted noise which has been induced into a video or audio signal by faulty earthing or grounding.
The process of assembling video clips, audio tracks, graphics and other source material into a presentable package.
Edit Decision List (EDL)
A list of all in points and out points for an editing task. Can be stored on a removable disc (eg. floppy disc). This enables an edit to be constructed in one edit suite, then taken to another (better) suite to make the final version.
Electronic News Gathering. This term was introduced with the evolution of video cameras for shooting news in the field (as opposed to film cameras). It is still widely used to describe mobile news crews.
The amount of light which is passed through the iris, and which the CCD or film is exposed to.
The process of adjusting selected ranges of frequencies in order to correct or enhance the characteristics of a signal.
A transition to or from "nothing". In audio, to or from silence. In video, usually to or from a colour such as black.
Half a video / television frame. A field comprises every second horizontal line of the frame, making a total of 312.5 lines in PAL and SECAM, 262.5 lines in NTSC.
Flying Erase Head
In video recorders, an erase head which is mounted on the drum assembly. The erase head wipes any previous recordings as new ones are made. "Normal" erase heads are stationary, and mounted to the side of the head drum. Because of their close proximity to the record heads, flying erase heads provide cleaner edits.
The distance from the centre of the lens to the camera CCD.
To adjust the lens in order to obtain a sharp, clear picture.
Frames Per Second. See also: Frame Rate.
(1) The edges of a television / video / film image.
(2) To compose a camera shot.
(3) One complete video, television or film picture. In video and television, each frame is divided into two interlaced fields. PAL and SECAM systems deliver 25 frames per second, with 625 horizontal scan lines. NTSC delivers 30 fps with 525 lines.
The number of video or film frames displayed each second (frames per second; fps). PAL frame rate is 25 fps, NTSC is 30 fps, film is 24 fps.
Measurement of aperture. The higher the f-stop number, the smaller the aperture.
A family of cable connectors, in which the centre (hot) pin is the centre wire of the cable itself.
(1) Chief electrician on a film set.
(2) Industrial-strength sticky tape, AKA duct tape.
(1) The volume level of an audio signal.
(2): The amplification level of a video signal.
(pronounced "gows", abreviation "G") Unit of magnetic induction.
(pronounced "jel") Semi-transparent heat-resistant material which is placed in front of a light source in order to modify it's colour temperature or other characteristics.
A satellite orbit in which the satellite remains in a fixed position above the Earth.
Person who is responsible for constructing and dismantling film sets, as well as laying down dolly tracks.
Any of the four non-metallic elements flourine, chlorine, bromine and iodine.
(1) The component which records an electrical signal onto magnetic tape, or reads a signal from tape into an electrical signal.
(2) The part which the camera is mounted on, atop a tripod, pedestal or other mounting. Allows the camera to pan and tilt.
The amount of space between the top of the subject's head and the top of the picture frame.
Unit of frequency. One cycle per second.
(1) An image or part of an image which is excessively bright, ie. overexposed.
(2) The wire in a cable, and the connecting pins, which carry the signal.
Hertz. Cycles per second
A digital video compression format.
Frequencies beyond the red end of the visible spectrum, ie. frequencies with longer wavelengths than red light. Perceived by humans as heat. Commonly used for remote-control devices.
The beginning point of an edit.
The point of contact between a tool and it's operator. A human/computer interface could be a keyboard or a mouse.
The method of dividing a video frame into two fields; one made up of the odd-numbered horizontal lines, the other made up of even-numbered lines.
A "closed-circuit internet". A local network of computers linked in much the same way as the wider internet.
The circular opening (aperture) which controls the amount of light passing through to the camera's sensing element or film.
A revolvable camera mounting arm, which can be attached to a dolly or crane.
Joint Photographic Experts Group. A standard for still-image compression.
A unit of temperature measurement. Colour is measured in degrees Kelvin.
In some forms of digital compression, uncompressed frames (key frames) are placed at regular intervals (eg. every 6th frame is uncompressed). Each subsequent frame exists as variations on the keyframe, until a new keyframe is introduced. The further apart the keyframes, the worse the overall picture quality.
Person in charge of constructing and dismantling film sets and dolly tracks.
Local Area Network.
A connection developed by Sony, used to link remote-control units, edit decks, etc.
A structure made of transparent glass or other material, with at least one curved surface, which causes the light rays passing through it to converge or diverge in a controlled fashion.
In video and television, the practice of placing black bars at the top and bottom of the frame, in order to simulate a wide-screen format (as if the viewer were looking through the slot in a letterbox).
That section of the electromagnetic spectrum which is visible, ie. perceptible to the human eye. Specifically, white light contains the wavelengths from 400nm (nanometres) to 700nm. Light travels through a vacuum at approximately 300,000 km (186,000 miles) per second.
A transducer which converts electrical signals into sound waves.
Measure of brightness
Professional tape formats from Panasonic. The M format was based on VHS technology, and was introduced at about the same time as Beta (in the mid-1980's). The MII format was introduced a few years later to compete with Beta SP. MII uses a different sized cassette.
Musical Instrument Digital Interface. A standard of communication between musical instruments, controllers and computers.
A camera framing term, half-way between a wide-shot and a close-up. A mid-shot of a person will show them from about the waist or chest up.
A device which accepts multiple signal inputs (video or audio), processes them, and provides one or more outputs. The outputs are "mixes" of the input sources.
To "change". A signal can be transmitted via a carrier wave, by modulating the wave to represent the signal.
A device used to view a video, graphic or text source, or to listen to an audio source. Video monitors use CRTs (cathode ray tubes), LCDs (liquid crystal displays), and other technologies. Audio monitors generally use cone drivers and horn divers, mounted in speaker cabinets.
Camera stand, like a tripod with one leg. Has the advantage of being light and easily portable.
A digital video compression format, based on the still image JPEG compression standard.
Computer-assisted process in which an image (or video) is gradually transformed into another.
Moving Picture Coding Experts Group. A digital video compression standard.
Neutral Density Filter.
Neutral Density Filter
A filter which reduces the amount of light coming through the camera lens, without affecting it's colour temperature.
Shots of the presenter / interviewer nodding, smiling, frowning etc. These can be shot after the interview and inserted during post-production.
Any method of video editing which doesn't require all shots to be assembled in a linear fashion.
National Television Standards Commission. Video/broadcast standard used in the USA, Canada, Japan, Mexico, and other countries. Delivers 525 horizontal lines of resolution at 30 fps (frames per second).
Out of action, not currently useable.
A "draft" edit, usually prepared in an off-line edit suite (at a lower cost), then taken to an on-line facility to make the final cut.
(2) In multi-camera or multi-tape set-ups, the camera or videotape machine which is currently selected by the director. For example, in an outside broadcast, the on-line camera is the camera which is currently live.
The final version of an edit prepared in a professional edit facility.
Optical Image Stabiliser
Circuitry in a camera that helps stabilize the image. Especially useful with hand held camera shots to reduce camera shake.
Dealing with properties of light.
Device which accepts an electrical input, and represents the variations of the input as a display on a CRT screen.
The end point of an edit.
A radio or television program that is broadcast from location, rather than from a studio.
Phase Alternate Line. Video/broadcast standard developed in Germany, and used primarily in Europe and Australasia. Delivers 625 lines at 25 fps (frames per second).
(1) Horizontal camera movement.
(2) The amount which a signal is divided between two pathways. For example, on an audio mixer, an input source can be panned across two stereo channels.
Pan Potentiometer. A component which pans a signal across two pathways. Typically a knob or slider. The knob on a domestic stereo which pans between left and right speakers is a pan pot.
A device capable of outputting various television test patterns. Used to test and calibrate vision equipment.
Pulse Code Modulation. A digital audio format.
The highest level of strength of a signal. If the "peak" or "clip" light on an audio mixer is activated, this means the respective bus (channel) is peaking at a dangerous level.
(1) A movable mount for studio cameras.
(2) The black level of a video signal.
A device which accepts a relatively low level audio signal, and boosts it to a level at which it can be output to a loudspeaker.
Disconnecting power from a device (usually by turning it off), in order to purge all charges and reset the device to it's default settings.
Peak Program Monitor.
The "lead-in" time at the beginning of a tape edit. When performing an edit, the tapes are rewound a few seconds, then played back before the edit begins. This ensures that the tapes are running at exactly the right speed.
Pressure Zone Microphone. AKA "boundary effect microphone". This type of mic uses a flat surface to pick up the pressure waves bouncing of a "boundary" such as the floor, a table, wall, etc. These mics are often used in conference situations - the mic lies flat and unobtrusive in the middle of the table.
A digital media format originally developed for the Apple Computer, but is now also available as "Quicktime for Windows".
Random Access Memory. A system of computer memory in which data can be retrieved in any order with equal speed.
(1) An American Broadcast Company.
(2) A small non-locking connector. Typically used in home entertainment systems.
Anything which occurs without delay. A real-time effects processor will add effects instantly, without having to wait to render.
The amount of detail in an image or signal. On a computer screen, the resolution is the number of pixels. In an analogue video signal, the resolution is the number of horizontal lines. In digital audio, the resolution is the number of samples per second. "Colour resolution" refers to the colour depth of an image, ie. how many colours are present.
The amount of time it takes an emitted sound to cease bouncing off objects such as walls.
Red, Green and Blue. The primary colours of video.
A near-instantaneous recording of a signal, measured in thousandths of a second. Digital signals are constructed by sampling analogue signals thousands of times per second. Each of these individual samples are strung together to make a close approximation of the original signal.
The level of colour in a vision signal. A highly-saturated signal has very strong colours.
All the shots which make up a segment of a program.
Systeme Electronique Couleur Avec Memoire. Video standard used primarily by France and various Eastern Bloc countries. Provides 625 horizontal lines at 25 frames per second.
Special Effects Generator. A device used to create special video effects.
Remote control of camera functions such as zoom and focus, by means of a motor. Servo controls can be mounted an the lens housing, on the tripod/pedestal handles, or on a remote-control unit.
The black level of a video signal.
A continuous piece of video or film footage. Everything you get between pressing "record" and "stop".
Signal Processing Device
Any device which takes a signal input, then modifies the signal before outputting it.
(Pronounced "simptee") Society of Motion Picture and Television Engineers. A groups which has set various video standards.
Random patterns of black and white dots on a TV screen or vision monitor. Snow can be caused by an improperly tuned television (or very poor reception), an unrecorded video tape, or dirty VCR heads.
A small light on a video camera which turns on when recording is in progress. In multi-camera situations; a light on a camera, or in it's viewfinder, which turns on when the camera is switched on-line or live.
Time Base Corrector.
(Prefix) Producing images or other results from a distance.
Material broadcast by television.
Magnifying lens, or combination of lenses.
Device which scrolls text on a screen, to provide cues for a television/video presenter.
To transmit by television.
Literally, vision at a distance. The transmission, reception, and reproduction of moving pictures and audio. Refers to both the process in general, and the receiving appliance.
Longer zoom, producing greater magnification.
Pattern of colours, lines and/or shapes designed to assist equipment calibration.
Vertical camera (framing) movement.
A device which adjusts, improves and corrects defects in a video signal. Can be used to synchronise different vision sources before being mixed together, to avoid picture disturbances when cutting from one source to another.
An audio test signal. Used to set signal levels, test signal quality, identify signal pathways, etc.
A device which coverts energy from one form into another. For example, a microphone is a transducer which converts acoustical energy into electrical energy.
A device used for switching or amplifying.
A device which converts video, audio and/or data signals into modulated radio frequency signals, and transmits them as radio waves.
A three-legged stand for mounting equipment such as a camera, etc.
Ultra High Frequency radio waves.
Audio frequencies above the upper limit of human hearing (approx 20,000 kHz).
An audio signal which consists of one "hot" signal plus the shield. This is common in home entertainment systems, as well as other systems with short audio cables. Unbalanced audio cables are prone to external interference, and are not preferred in professional situations.
A filter which blocks out a certain percentage of ultra-violet light.
A multi-electrode valve which controls the flow of electrons in a vacuum from electrode to electrode.
Video Cassette Recorder.
A graphics image which exists as a series of geometric shapes, rather than as a series of values for each pixel. Has the advantage of being resizable without loss of quality.
A device which graphically displays information about the chroma (colour) part of a vision signal. Used in conjunction with a waveform monitor (in fact, many devices are switchable between waveform and vectorscope modes).
Very High Frequency. This is a popular television broadcast band. It is lower than UHF (Ultra-High Frequency), and generally has a higher broadcast range.
Vertical Helical Scan. In the late1970's, VHS became known as Video Home System, but this is merely a marketing name. VHS won the format war against Betamax, despite being technically inferior. There are many arguments about why VHS won, mostly involving availability of movies and licensing issues.
The strength of a video signal. Level is measured in volts/millivolts - the standard broadcast vision level is 1V peak-to-peak, of which 700mV comprises the picture information and 300mV comprises the timing and sync information.
A component of video, television and film cameras. Available as EVF (Electronic Viewfinder) or OVF (Optical Viewfinder). An EVF has a small CRT which displays the camera output (or tape output).
The picture component of a video, television or film program (as opposed to the audio component).
Vision Control Operator
The person responsible for maintaining the technical quality of the vision signals. This may involve controlling some camera's functions remotely (such as iris, colour balance, etc.), as well as making adjustments to any vision source's technical characteristics (such as video level, timing, etc.).
(1) A device which accepts multiple vision source inputs, manipulates them, and provides one or more vision outputs in real time.
(2) A person who operates a vision mixer. AKA vision switcher.
(Pronounced "vitsee") Vertical Interval Time Code.
Of the human voice.
Unit of electromotive force. 1 volt, when applied to a 1 ohm conductor, produces a current of 1 ampere.
Electromotive force, in volts.
A device which measures voltage. One of the functions of a multimeter.
(1) Voice operated switch.
(2) Abbreviation for vocals.
From the latin phrase vox populi, meaning "voice of the people". The vox pop is a technique used in many forms of media, to provide a "snapshot" of public opinion. Random subjects are asked to give their opinion on a particular topic, and these are presented to the viewer/reader as a reflection of popular opinion.
Video Tape Recorder.
Unit of power; equivalent to one joule per second. 1 watt (W) = 1 volt (V) x 1 amp (A)
Amount of electrical power, in watts.
An oscillation which is propagated from place to place.
The shape (form) of a wave, or a representation of this form.
An oscilloscope specifically designed to display the waveforms of video signals. Used to monitor signal strength, sync timing, etc.
The distance between any point on a wave and the equivalent point on the next phase.
A camera function which gives a reference to "true white", in order for the camera to interpret all colours correctly.
Generally refers to any aspect ratio greater than 4:3.
Wide Shot (WS)
A framing term, meaning a camera shot which shows the whole of the subject.
A transition in which parts of one shot are successively replaced by equivalent parts of the next shot.
A very fast camera pan, usually such that individual frames are severely blurred.
Wavering of audio reproduction, due to speed fluctuations.
A lockable connector, available with various numbers of pins (the most common being the 3-pin XLR). Often referred to as a "Canon", after the popular manufacturer of XLR connectors.
Luminance. The "brightness" of a signal.
Luminance/chrominance. A video signal which consists of two signals - the luminance (brightness) and chrominance (colour). This type of signal is used in S-VHS and Hi-8 formats.
AKA "Split lead". A lead with one connector at one end, and two at the other. For example, a mono audio output could be split (using a y-lead) into two signals, to be plugged into the left and right inputs of another device.
A feature of professional cameras, which places diagonal lines across any over-exposed parts of the picture in the viewfinder. These stripes will not show on the output/recorded picture, they are only there as a guide for the camera operator.
Framing movement, in which the focal length of the zoom lens is altered to make the subject appear closer to, or further away from the camera. Note that this effect is similar, but not the same as moving the camera itself closer to or further away from the subject.
A lens with a moveable element, which is able to "zoom" between various focal lengths. This has the effect of making the subject appear closer to, or further away from the camera. There are two main zoom control mechanisms available:
(1) Servo zoom. This is a lever which usually sits on the lens housing. It's positioned so that when you slide your right hand into the grip belt, the servo zoom will be sitting under your first two fingers. Pressing the front part of the lever zooms in, pressing the rear part zooms out. Cheaper cameras usually have a constant zoom speed, whereas a good servo zoom will have variable speed - the further you depress the lever, the faster the zoom. The lever may have labels such as T and W (tele and wide). "Remote zoom" and "zoom demand" mechanisms are also available for professional cameras, enabling the zoom to be controlled from a separate lever. This lever may be wired to the camera, or connected via infra-red control.
(2) Manual zoom (ring). This is a zoom ring on the lens housing which is rotated manually, typically by the left thumb and index finger.