The process of altering the frequency bands of a video signal to
compensate for the loss of high
frequency in a cable. The video equivalent to a graphic equalizer
in a stereo system.
CAD. Computer Aided
Design. This usually refers to a design of system that uses
specialized software to model reality
in a controllable fashion.
Candela [cd] (or candle power).
A unit for measuring luminous intensity. The modern definition is
The candela is the luminous intensity,
in a given direction, of a source that emits monochromatic
radiation of frequency 540 ×
1012 hertz and that has a radiant intensity in that direction of
1/683 watt per steradian.
The frequency chosen is that to which the eye is most sensitive.
This frequency is normally referred
to as the corresponding wavelength: 555 nanometer. The
strange choice of the number 683
is to make the value identical to that obtained with the previous
version of the unit: the emission
from 1 square centimeter of glowing, solidifying platinum.
The old definition is :-
One candela is approximately equal to the amount of light energy
generated by an ordinary candle.
Since 1948 a more precise definition of a candela has
become: "1/60 of the light emitted
from 1cm2 of the surface of a
the temperature at which platinumconverges
from a liquid state to
a solid (i.e. freezes)."
CATV. Community Antenna
C-band. A range of
microwave frequencies, 3.7~4.2 GHz, commonly used for satellite
Device. A "bucket brigade" shift register device which when
with photodiodes is the modern
imaging device, replacing the old tubes. When first
the 1970s, it was designed to be
used as a memory device, as an analogue shift
Most often used in cameras,
but also in telecine, fax machines, scanners, etc.
CCD Iris. A term used
by some manufacturers to describe automatic shutter control, to
changes of lighting in a scene, without having any moving parts.
Consultatif International des Radiocommuniqué, which is the
standardization body that has set
the standards for television in Europe. It was initially
monochrome; therefore, today the
term CCIR is usually used to refer to monochrome
cameras that are used in PAL countries.
CCIR 601. An
international standard (renamed ITU 601) for component digital
that was derived from the SMPTE
RP1 25 and EBU 3246E standards. ITU
601 defines the
sampling systems, matrix values
and filter characteristics for Y, Cr, Cb and
digital television. It establishes
a 4:2:2 sampling scheme
at 13.5 MHz for the luminance
channel and 6.75MHz for the chrominance
channels with eight bit
digitizing for each channel.
These sample frequencies werechosen
because they work for both 525 line 60Hz and 625 line
50Hz component videosystems.
The term 4:2:2 refers to the ratio of the number of luminance
channel samples to the number of
chrominance channel samples; for every four luminance
samples, the two chrominance channels
are each sampled twice.
CCITT Committée Consultatif
Internationale de Telegraphique et Telephonique. The
now known as the ITU-T (for Telecommunication
Standardization Sector of the International
Telecommunications Union), is the
primary international body for fostering co-operative
standards for telecommunications
equipment and systems. It is located in Geneva, Switzerland.
CCTV. Closed Circuit
TeleVision. A television system intended as a "closed" system,
than broadcast, to be viewed by
only a very limited number of viewers e.g. 1 camera to 1
monitor in its simplest form.
CCTV camera. A unit
containing an imaging device that produces a video signal in the
form, usually with synchronization
pulses and colour information (composite video).
A CCTV system, or an associated group of systems, together with all
necessary hardware, auxiliary lighting,
etc., located at a site to be monitored.
CCTV system. An arrangement
comprising of a camera and lens with all ancillary equipment
required for the surveillance of
a specific area.
CCVE. Stands for Closed
Circuit Video Equipment. An alternative acronym for CCTV
created by a manufacturer.
CD. Compact Disc.
A standard of media as proposed by Philips and Sony, where music is
stored in digital form.
CD-ROM. Compact Disk
Read Only Memory. The total capacity of a CD-ROM when storing
data is up to 700 MB (including
CDS. Correlated Double
Sampling. A technique used in the design of some CCD cameras that
reduces the video signal noise
generated by the chip.
Celsius. The Systeme
Internationale (SI) unit of temperature equivalent to the Centigrade
It does not use the prefix "degrees".
CFA. Colour Filter
Array. A set of optical filters (usually individual pixel sized)
used in single chip
colour CCD camerasto produce the
colour components of a video signal.
Chip. An integrated
circuit in which all the components (resistors capacitors and
are micro-fabricated on a tiny
piece of silicon or specialist
material (silicon on sapphire). Often
used to refer to the detector in
a CCD camera.
Chroma Burst. See Colour
Chroma crawl. An artefact
of encoded video, also known as dot crawl or cross-luminance.
It occurs in the video picture
around the edges of highly saturated colours as
a continuous series
of crawling dots and is a result
of colour information being confused as luminance
by the decoder circuits.
Chroma gain (chroma or colour,
saturation). In video, the gain of an amplifier as it
of colours in the active picture.
Chroma key (colour key).
A video key effect in which one colour or video signal is inserted in
place of all areas of a particular
colour in another video signal.
Chrominance. The colour
information of a colour video signal.
(crosstalk, cross-modulation). An undesirable
change in luminance amplitude caused
by superimposition of some chrominance
on the luminance signal.
Appears in a TV picture as unwarranted brightness
by changes in colour saturation
CIE. Commission Internationale
de l'Eclairagé. This is the International Committee for
established in 1965. It defines
and recommends light units.
CIE Model. A colour
model based on human perception developed by the CIE (Commission
Internationale de l'Eclairage)
committee. While widely regarded as the most accurate colour
model, CIE is unsuitable for many
technologies, including colour printing and colour monitors.
Consequently, these systems need
to use other colour models, such as CMYK and RGB. There
is a growing trend, however, to
make all colour models relative to the CIE model. This would
make it easier to translate from
one model to another.
CIF. Common Intermediate
Format. A video format used in videoconferencing systems
supports both NTSC and PAL signals.
CIF is part of the ITU H.261videoconferencing standard.
It specifies a data rate of 30
frames per second (fps), with each frame containing 288 lines and 352
pixels per line. A
related standard, QCIF (Quarter CIF),
one fourth the amount of data
and is suitable for videoconferencing
systems that use telephone lines.
Clamping (DC). The
circuit or process that restores the DC component of a signal. A
clamp circuit, usually triggered
by horizontal synchronizing pulses, re-establishes
a fixed DC
reference level for the video signal.
DC clamping can, in some cases remove of
low-frequency interference, especially
Cladding. The outer
part of an optical fibre cable, which is also glass but with a different
refractive index to the central
core. It enables "total internal reflection" so that
the central core stays, inside that core.
Clipping Level. An
electronic limit to avoid overdriving the video portion of the
C-mount. Cine mount.
The first standard for CCTV lens screw mounting. It is defined
the thread of 1''
(25.4 mm) in diameter and 32 threads/inch, and the back flange-to-CCD
distance of 17.526 mm (0.69'').
The C-mount description applies to both lenses
C-mount lenses can be put on both,
C-mount and CS-mount
cameras, but must use a C-mount
adaptor when used on a CS-mount
camera. If a C adaptor is used on a C-mount camera the
image will only focus at very short
range, it can then be considered as an economy macro
C-mount adaptor. An
adaptor used to convert a CS-mount camera to C-mount to accommodate
a C-mount lens. It is simply
a ring 5 mm thick, with a male thread
on one side and a female
on the other side. It has
a 1'' diameter and 32 threads/inch, as the cameras and lenses. It
comes packaged with the newer type
(CS-mount) of cameras.
CMYK. A 4 colour encoding
system used by many computer printers, in which colours are
expressed by the
"subtractive primaries" (cyan, magenta
and yellow) plus black (called K). The
black layer is added to give increased
contrast and range.
Coaxial cable. The
most common type of cable used for copper transmission of video signals.
It has a coaxial (sharing the same
axis) cross-section, where the centre core is the signal
conductor, while the outer shield
protects it from external electromagnetic interference.
An encoder plus a decoder is an electronic device that compresses
and decompresses digital signals.
It is also used to refer to conditional refresh video equipment.
Colour bars. A pattern
generated by a video test generator, consisting of eight equal width
colour bars. Colours are
white (75%), black (7.5% setup level), 75% saturated
pure colours red,
green and blue, and 75% saturated
hues of yellow, cyan and magenta
(mixtures of two
colours in 1:1 ratio without third
colour). The colours appear in the order White, Yellow, Cyan,
Green, Magenta, Red, Blue, Black.
carrier. The sub-carrier frequency in a colour video signal
MHz for PAL &
3.58MHz for NTSC) that is phase
modulated with the colour information. The colour carrier
frequency is chosen soits spectruminterleaves
with the luminance spectrum with minimum
interference. This signal
is superimposed on the
luminance level. The amplitude of the colour
saturation and phase
angle represents hue.
Colour difference signal.
A video colour signal created by subtracting luminance and/or colour
information from one of the primary
colour signals (red, green or blue). In the
difference format, for example,
the luminance (Y) and colour difference components
(R-Y and B-Y) are derived as follows:
Y = 0.3 Red + 0.59 Green + 0.11
R-Y = 0.7 Red - 0.59 Green - 0.11 Blue
B-Y = 0.89 Blue - 0.59 Green - 0.3 Red
The G-Y colour difference signal
is not created because it can be calculated from the other
three signals. The colour
difference signals are, sometimes, wrongly referred to as component
That term is reserved
for the RGB colour components.
Colour phase. The
timing relationship in a video signal that is measured in degrees and
the hue of a colour signal correct.
Indicates the hue of the colour. It is derived from photography
spectrum of colours is based upon
a comparison of the hues produced when
a black body
(as in Physics) is heated from
red through yellow to blue, which is the hottest.
temperature measurements are expressed
in Kelvin (not degrees Kelvin).
Comb filter. An electrical
filter circuit that passes a series of frequencies and rejects the
frequencies in between, it combs
out the frequencies. Used on a composite video signal, to
separate the chrominance signal
and reject the luminance signal,
or to select the luminance
signal and reject the chrominance
signal. This filter is found in S-VHS VCRs to separate the
chrominance and luminance so that
a composite video input can be recorded in S-VHS
format. These filters can
also be found in some multiplexers to give a Y - C output for
recording on an S-VHS recorder.
Composite sync. A
signal consisting of horizontal sync pulses, vertical sync pulses and
equalizing pulses only, with a
no-signal reference level.
Composite video signal CVS.
A signal in which the luminance and chrominance information
combined using one of the coding standards NTSC, PAL, SECAM,etc.
Concave lens. A lens
that has negative focal length, i.e., the focus is virtual (in front of
lens) and it reduces theobjects.
A concave lens cannot project an image.
Contrast. A common
term used in reference to the video picture dynamic range, i.e., the
difference between the darkest
and the brightest parts of an image.
Convex lens. A convex
lens has a positive focal length, i.e., the focus is real (behind the
It is usuallycalled magnifying
glass, since it magnifies the objects. It can be used to project
CPU. Central Processing
Unit. A common term used in computers.
CRO. Cathode Ray Oscilloscope
Crosstalk. A type
of interference where one signal is present in some measure on a second
signal in a system. The amount
of crosstalk is measured as a ratio and expressed in dB. It
can be caused by unintentionalcapacitance
(AC coupling) or more commonly by bad Earth
connections on a connector panel.
CRT. Cathode Ray Tube.
A vacuum tube used for visual displays.
CS-Mount. Cine Short
mount. The newer standard for lens mounting. It uses the
physical thread as theC-mount,
but the back flange-to-CCD distance is reduced to 12.5 mm.
The lenses are smaller, more compact
and less expensive. CS-mount lenses can
used on CS-mount cameras.
CVBS. Composite Video
Burst Signal. In broadcast television this refers to the video
including the colour information