Glossary of Video Terms
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Select the first letter of the word to jump to appropriate section of the glossary.


- A -

 
Active Video Lines

All video lines not occurring in the horizontal and vertical blacking intervals.
 
AFC

Abbreviation for automatic frequency control, a circuit built into some
VCRs and TVs to automatically lock onto an incoming channel.
AFM

Audio frequency modulation is the type of audio recording used on
Beta HiFi
and VHS HiFi VCRs. The audio is laid on the tape by audio
heads located on the video head assembly.
 
AGC

Abbreviation for automatic gain control. On a TV or VCR, AGC is a
circuit
that automatically adjusts the incoming signal to the proper
levels for display or recording. On a video camera, AGC is a circuit
that automatically adjusts the sensitivity of the pickup tube to render
the most pleasing image.
 
Alarm Activated VCR

After pressing 'record'', a normal VCR takes about 20 seconds before
it starts recording usable pictures. With and alarm activated recorder
it can be set so that the tape is ready to start recording in about one
second. The signal to begin recording can be from an alarm or any
other input.
 
Aperture

The light gathering area of a lens, controlled by the iris.
 
Aspect Ratio

The ratio of the vertical to the horizontal image size. This is usually 3:4.
 
Attenuation

This refers to signal loss in a transmission system
 
Audio S/N Ratio

Signal-To-Noise Ratio is the ratio of pure audio signal versus noise.
 
Automatic Iris

A lens that adjusts automatically to allow the right amount of light to
fall on the imaging device. There is a tiny motor and amplifier built in
which receives a control signal from the camera to maintain a
constant one volt peak to peak
(1.0 Vp-p) video level.
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- B -

 
Back Focus

A mechanical adjustment in a camera that moves the imaging device
relative to the lens to compensate for different focal lengths of lenses.
This is important when a zoom lens is fitted.
Balanced Signal

A video signal is converted to a balanced signal to enable it to be transmitted
along a 'twisted pair' cable. Used in situations where the cabling distance is too great.
 
Bandwidth

The range of signal frequencies that a piece of audio or video equipment
can encode or decode; the difference between the limiting frequencies
of a continuous frequency band. Video uses higher frequency that
audio, thus requires a wider bandwidth.
 
BetaCam & BetaCam SP

BetaCam was first introduced in 1982. It is currently geared for broadcast use, although there have been some less expensive models destined more for industrial use. Pictures you will get using a BetaCam system (or other component format) will generally be markedly superior to those you would get using any of the preceding formats. Colors in particular come out looking much more vibrant and objects appear three-dimensional. The superiority of BetaCam shots comes partly from the technical aspects of the tape format but also in large part because of the use of superior optics and other camcorder and VTR components (and generally better operators!).
The difference between BetaCam and BetaCam SP, introduced in 1986, is in the tape. Betacam SP uses a metal tape and is an improvement over BetaCam.
BetaCam cassettes are large. Ninety minute cassettes measures 5.5 by 10 inches (14 by 25 cm). Typically BetaCam field units (camcorders or dockable decks) handle only smaller cassettes with shorter lengths of tape (30 minutes and less). These smaller cassettes are 4 by 6 inches (10 by 16 cm) in size.
 
Betamax

Betamax tapes were a format originally introduced by Sony in the 80's. It was thought to be a better format at the time. However, the Beta vs VHS wars took place and VHS was the victor. There are still a few Beta fans out there though and you can still get a Betamax machine if you look around.
Blooming

Picture distortion caused by a high video level. Blooming results when the
image sensor of the video camera picks up a very bright subject or an area
with high illumination.
Burst

A component of a television signal that carries color information.
 
Brightness

In color video, the characteristics that makes pictures appear to be most
intense, created by luminosity; also the quality of being filled with light.
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- C -

 
C-Mount

The standard screw mounting for 2/3" and 1" camera lenses. The distance
from the flange surface to the focal point is 17.526mm. A C-Mount lens can
be used on a camera with a CS-Mount by adding adapter ring to reduce the
distance to 12.5mm.

CS-Mount

A new generation of lenses designed for 2/3", 1/2" and 1/3" cameras incorporating CS-mounts. The distance from the flange surface to the focal point is 12.5mm. CS-mount lenses cannot be used on cameras with C-mount configuration. These lenses are smaller and cheaper than the C-mount equivalents.
 
CATV

An abbreviated term for Community Antenna Television, now generally
regarded as "cable TV".
 
CCD

Charged-Couple Device used in some video cameras instead of an image
pickup tube. Light-sensitive microprocessor that converts an image into an
electrical flow. CCDs are not prone to image smear or lag and make light
weight cameras possible.
 
CCIR

Committee Consulat International Radiotelegraphique. This is a standards
committee of the International Telecommunications Union, who have made
the technical recommendation for European 625 line standard for video signals.
 
Chroma

Short for chrominance. Chroma is the color component of the video signal.
 
Clipping

An effect of distortion where the peaks of driven signals are chopped off.
Clipping usually occurs in the amplifier when it is turned up too high, but it
can occur in maladjusted circuits in a VCR or TV set.
 
Color Burst

The signal, at approximately 3.57MHz in the video bandwidth, that stores the instantaneous intensity and hue of the color for a particular spot in the TV image.
 
Comb Filter

An electric filtering system designed to pass a certain set of frequencies but
reject others.
 
Composite Video

A picture signal combined with synchronization and (possibly) color
information. Usually called baseband video, or just video.
 
Control-L


Also referred to as LANC, this is a control protocol found on 8mm and some
VHS decks that provides computer control of unit operation. Units are
connected through a special cable.

 
Control Track

A linear track, consisting of 30- or 60-Hz pulses, placed on the bottom of
videotape that aids in the proper playback of the video signal.
 
Convergence

Three colors-red, blue, and green-are used in television to produce all colors.
These separate scanning beams (one for each color) must strike their targeted phosphors (screen's internal coating) with precise accuracy. If the beams are out of alignment, then the image and colors appear muddied.
 
Crosstalk

A signal from one stereo channel that bleeds into the other. Also, a signal
from a video track on a tape bleeding into the signal on the adjacent track.
 
CRT

Cathode Ray Tube. The main part of a normal monitor or television.
AKA the screen.
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- D -

Decibel (dB)

A unit of power measurement. A 6 dB rise in signal strength represents a
100-percent increase (or doubling) in power.
 
Demodulate

To remove the carrier signal and leave only baseband audio and video.

Depth of Field

The are in which all objects picked-up by the camera lens appear in focus.
Depth of field depends on subject-to-camera distance, focal length of the
lens, and f-stop.
 
Digital 8

The DIGITAL 8 format is far superior to HI-8 or 8MM. Sony was the first to introduce this format and has done a great job. It is backwardly compatible, meaning that the new Digital8 camcorders and VCR's will also play your 8MM and HI-8 tapes. You do not have to buy special tapes to record in Digital8. A regular 8MM or HI-8 tape will record up to 60 minutes of digital video and audio. Because of the design, using regular tapes is not a problem, but it uses twice as much tape. A 2 hour HI-8 or 8MM tape will record 60 minutes when done in the Digital mode. For more information on Digital8, Click Here.
Digital Signal

An analogue signal that has been converted to a digital form so that it can be processed with less error.
DNR

Dynamic Noise Reduction.
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- E -

EIA

Electronic Industry Association. An industry lobbying group; it collects
statistics and establishes testing standards for many types of home electronics.
 
EIAJ

Electronics Industry Association of Japan. The Japanese equivalent of the EIA.
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- F -

F-Connector

The standard connector used with coaxial cable and the RF inputs/outputs
of most video equipment.
 
Field

One-half of a video field, comprising the odd or even scan lines. There are
60 fields in one second of video.
 
Flagging

Bending at the top of a picture played back by a VCR.
 
Focal Length

The distance between the secondary principal point in the lens and the plane of the imaging device. The longer the focal length, the narrower is the angle of view.
Footcandles

(Ft-c) Lumens per square foot; the measurement of the intensity of light on
a camera.
 
Frame

One complete video picture, comprising both odd and even fields. There
are 30 video frames per second.
 
Frame Store

An electronic method of capturing and storing a single frame of video. All slow scan transmitters include a frame store that holds the picture at the moment of alarm, while the control is being dialed up. When the link is confirmed, the picture is transmitted
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- G -

Gain

The level of amplification of a signal.
 
Gen-Lock

Alignment of the sync generators of one or several sources to main sync
source. Used in multi source camera shoots or editing.
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- H -

Helical Scan

The technical name for the way the video heads in a VCR record and play
back picture information. Also used to record and play back stereo HiFi audio.
 
HI-8

HI-8 camcorders record their signal at about 400 lines of resolution, slightly less than Mini DV, but substantially higher than 8mm or regular VHS formats. Most often, HI-8 camcorders record sound in hi-fi stereo. Slight quality loss is suffered when copying or editing from HI-8, but a better than average image is maintained. Tapes from HI-8 camcorders generally must be played using the camera as the source, which means the user often must connect cables to their television or VCR.   HI-8 tapes can be bought in 30, 60, and 120-minute lengths.
 
Horizontal Resolution

The number of vertical black and white lines that can be defined, as measured along a horizontal line.
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- I -

IR

Abbreviation for infrared.
 
Image Enhancer

Electronic device that smoothes out irregularities in a video signal to
improve picture definition.
 
Impedance

The degrees of resistance that an alternating electrical current (ac)
encounters when passing through a circuit, device, or wire. The
amount of impedance is expressed in ohms.
 
Infrared Light

The wavelength of light produced above the visible part of the spectrum.
Interlace

Each television frame (30 per second) or individual picture is comprised of two fields (A and B). These two fields seem to appear at once on the TV screen, but each field is scanned separately in the picture or image-creation process. Each field contains 260 lines of picture information. How well these lines are interlaced determines the resolution of the resulting picture.
 
Internal Sync

The internal generation of sync pulses in a camera using a crystal controlled
oscillator. This is needed on non-mains powered cameras.
Iris

Adjustable lens opening that regulates amount of light entering the camera.
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- J -

 

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- K -

 

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- L -

Line Locked

The sync pulses of cameras are locked to the AC mains frequency.
 
Line Powered

A camera in which the power is supplied along the same coaxial cable that carries the video signal.
 
Loop Frame Store

The principal is that a series of video frames is compressed and stored in a continuous loop. This records a certain number of frames and then records over them again until an alarm signal is received. When this happens it carries on recording for a dozen frames or so and then stops. This means that frames before and after the incident are recorded. This eliminates the boring searching through hours of video tape and concentrates on the period of activity.
Luminance

The term used to denote the brightness or black-and-white picture of a video image.
 
Lux

A measurement of illumination. The metric equivalent of footcandle.
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- M -

Macro-Focus

Some zoom lenses include this feature, which allows you to get as close as one or two inches to your subject. This is a great feature for video taping small objects such as coins, stamps, or insects.
 
Macro-Lens

Lens capable of close-up focusing.
 
MII

Introduced in 1986, MII is Panasonic's answer to Betacam SP. All MII tape is metal. The 90 minute cassette at 4 by 8 inches (11 by 19 cm) is considerably smaller than the 90 minute Betacam SP cassette. However the dockable decks take only a small 20 minute cassette (3.6 by 5 inches - 9 by 13 cm). Technically, MII is equal to or superior to Betacam SP. Panasonic MII field equipment includes several small dockable decks usable with a variety of camera heads and some excellent portable decks.
Be aware if you get into MII that at some point repairs may become an issue and that few duplicating facilities or clients are likely to have MII. Therefore you will probably have to copy your MII programs to another format at some stage.
Mini DV

Mini DV tapes are the smallest of the video formats. They take and maintain crystal clear images because of the nature of a digital format. Editing enthusiasts benefit from Mini DV as well, since copying between two units is done with no quality loss. That means edited or copied video looks and sounds every bit as good as the original footage. Mini DV tapes are available in 30, 60 and 63 minute lengths.  You can also have Mini DV tapes transferred to VHS. For more information on Mini DV, Click Here.
Modulation

A way in which one signal modifies or controls another signal for such
purposes as enabling it to carry information. Often used to describe radio
frequency (RF) transmission. FM is a frequency modulation; AM is
amplitude modulation.
 
Monitor

A video display. A monitor is like a TV except it lacks the ability to tune in
channels. A monitor may or may not have a sound amplifier and speaker.
 
Monochrome

Black and White.
 
Multiplexor

An electronic system that can accept a number of camera inputs and record
them virtually simultaneously. They can also provide multi screen displays
with four, nine, sixteen etc. cameras on the screen at once. Mulitplexors can be used to transmit multiple pictures down a single video line whether it is a coaxial cable, microwave, infrared link etc. This requires a multiplexor at each end of the line.
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- N -

Noise Bars

White streaks in a picture, usually caused when video heads trace parts
of the tape that have no recorded signal, also known as guard bands.
 
NTSC

National Television Standards Committee. A group of businesses and
engineers originally created to decide on early standards for color and black-
and-white televisions in the U.S.. The NTSC system is also used in Japan.
Other television standards around the world include PAL (most of Europe) and SECAM (France, parts of Africa and Russia).
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- O -

Overscanning

A technique used in consumer display products that extends the deflection of a CRT's electron beam beyond the physical boundaries of the screen to ensure that Images will always fill the display area. See also underscanning
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- P -

PAL

Phase Alternate by line is the 625-line color video system currently used in
most of Western Europe, England, Australia, and South Africa.
 
Pan Tilt Zoom (PTZ)

A device that can be remotely controlled to provide both vertical and horizontal movement for a camera, with zoom.
PCM

Abbreviation for pulse code modulation, a way of digitally recording an audio
signal. Used in most 8mm decks and in some high-end VHS and S-VHS decks.
 
Peak to Peak

The measurement of any signal from the lowest value to the highest. In a composite or full video signal, this should be 1 Volt.
 
Pixel

Picture element.
 
Pre-Set Controller

A function contained within a telemetry system that, on receipt of a signal, causes a particular camera to pan, tilt and zoom to a predetermined field of view. Most systems can accommodate up to sixteen preset positions for each camera. This is an especially useful feature on larger systems with alarmed areas.
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- Q -

Quad Screen

Display where 4 cameras are viewed on the same screen, each camera image occupying a quarter of the display area. Other 'multi-screen' modes are possible such as 9, 16 and 25 way. The splits do not always have to be equal and other configurations can be possible.
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- R -

Real Time Recording

Refers to the top speed of a video recorder; governed by the monitor - pictures are available as fast as the video can accept them.
 
Remote Switcher

A video switcher which is connected to the camera cables and which contains the switching electronics. This unit may be remotely located and connected to a desk top controller by a single cable for each monitor.
Residual Color

This is the amount of color in the image of a white target after a color camera has been white balanced. The less color, the better the camera.
 
Resolution

The clarity or sharpness of the picture. Resolution is most often stated in
the number of total lines that make up an image or in MHz.
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- S -

Saturation

The strength or amount of a certain color present in a television picture;
saturation is expressed as the purity of the color.
 
Scene Illumination

The density of light falling on the area to be viewed. For best results the ratio
of the lightest to the darkest areas should not be more that a factor of two.
 
Screen Splitter

A term usually used for a device that can combine the views from two cameras on a single screen. Normally the camera syncs need to be locked together.
S/N Ratio

Signal-to-Noise ratio is the amount of desired signal as compared to
undesired signal. In video Tape, noise appears as "snow," audio noise is
the tape hiss heard upon playback. A way of measuring how good a
picture or a sound will be.e The higher the ratio between the desired type of
signal and the unwanted noise, the better the results.
 
S-VHS or Super VHS

A VHS format that enables recording and playback of very high resolution
video. The format uses a 4 pin din cable to carry the separated signals,
chrominance and luminance, versus the composite type that combines
the signal over one wire.
 
S-Video

Type of video signal used in the Hi8 and SVHS videotape formats. S-Video
transmits luminance and colour portions separately, using multiple wires, thus avoiding the colour encoding process and its inevitable loss of picture quality.
 
Switcher

A simplified SEG that selects and mixes video signals from two or more sources.
 
Sync

Short for synchronization, a broad term to indicate the proper order of
electrical signals to generate and display sound and picture from a videotape.
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- T -

 
Telemetry

The system by which a signal is transmitted to a remote location in order to control CCTV equipment e.g. to control pan and tilt and zoom functions, switch on lights, move to preset positions etc. The controller at the operating position is the transmitter and there is a receiver at the remote location. The signal can be transmitted along a simple 'twisted pair' cable or along the same coaxial cable that carries the video signal.
 
Television & Film History

A
history of Film & Television can be found Here.

Terminating Resistor

A resistor (usually 75 ohms) attached to the end of a cable or to an input
or output on a piece of video equipment. The resistor restores proper system
impedance.
 
Test Patterns

A
test pattern is used to check out video systems, cameras and control equipment. Several examples can be found Here.
 
Time Lapse VCR

A type of video recorder that can be set to record continuously over long periods. This can be anything from three hours to 480 hours, achieved by the tape moving in steps and recording one frame at a time. This means that if set to record over long periods much information can be lost. On receipt of an alarm signal these machines can be automatically switched to real time mode.
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- U -

U-Matic

U-Matic also known as 3/4" video tape. The format was introduced in 1971 but it is still used by some videographers who have been using the format for a long time. It can produce good quality video and 3/4" decks are still commonly available in duplicating houses. However, there is little reason for somebody to persue this format given the technical advantages of some of the other more recent formats. UMatic has been used by professionals the world round and found mostly in studios. The format is slowly being replaced with digital equipment such as DV and Mini DV.
Underscanning

A technique generally used by some TV and video systems as a way of ensuring that the complete image is always visible within a display area; the opposite of overscanning.
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- V -

VHS & VHS/C

Abbreviation for video home system, a VCR format pioneered by JVC. VHS/C and full size VHS record at a slightly lower resolution than 8MM. Their appeal, or course, is the convenience of easy playback. The large VHS camcorders are almost a thing of the past at this point. There are still a few models available, but their substantial size and weight make them a difficult sell against smaller camcorders. VHS/C compact models, on the other hand, remain a popular choice, offering many of the same key features as 8MM camcorders, at an equally affordable price.

 

Video Motion Detector

A method of detecting movement in the view of the camera by the electronic analysis of the change in picture contrast.
VU

Volume Unit is measured by sound-level meter. VU meters are usually
marked from -20 to +5 Vus. O Represents the loudest level before
distortion occurs.
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- W -

White Balance

Assures the correct balance of red, green, and blue. Because these
colors are used to create all other colors in television, white balancing a
camera enables you to bring the colors in line for the existing lighting
conditions. Also refers to a camera control that accurately sets light levels
on a white surface.
 
Wide Angle

The wide-angle position of a lens enables the lens to capture a wider area
of view. Be careful when video taping people with a wide-angle lens at close
range.
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- X -

 

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- Y -

Y/C Video

See S-Video
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- Z -

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