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Active Video
Lines - All video lines
not occurring in the horizontal and vertical blacking intervals.
AF
- Abbreviation for automatic frequency
control, a circuit built into some VCR's 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 VCR's. 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.
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.
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 thedistance 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.
D
Decibel
(dB) - A unit of
power measurement. A 6 dB rise in signal strength represents
a 100-percent increase (or doubling) in power.
Demodulat - 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 thelens, 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.
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. 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.
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
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.
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.
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.
J
K
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.
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.
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 isamplitude 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.
MPEG4 - Moving
Picture Experts Group. A standard for digital video &
audio compression.
Multiplexer - 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.
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).
O
Overscanning - A technique used in consumer
display products that extends the deflection of a CRT's electron
beam beyond thephysical boundaries of the screen to ensure that
Images will always fill the display area. See also underscanning.
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 audiosignal.
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.
- 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.
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.
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.
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.
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.
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.
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.
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.
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.
X
Y
Y/C
Video - See S-Video
Z
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