Movie kya hai, kya ye bhe tisveer hai,ya aks hai, Ulma Ahle Sunnat ki ktub ke hawaly or Akabar Muftiaan Ahle Sunnat ke Fatwaon ki roshani main Video Ka Istamall jazz sabit kya gya hai.
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III THE TELEVISION CAMERA
The television camera is the first tool used to produce a television program. Most
cameras have three basic elements: an optical system for capturing an image, a
pickup device for translating the image into electronic signals, and an encoder for
encoding signals so they may be transmitted.
A Optical System
The optical system of a television camera includes a fixed lens that is used to
focus the scene onto the front of the pickup device. Color cameras also have a
system of prisms and mirrors that separate incoming light from a scene into the
three primary colors: red, green, and blue. Each beam of light is then directed to
its own pickup device. Almost any color can be reproduced by combining these
colors in the appropriate proportions. Most inexpensive consumer video cameras
use a filter that breaks light from an image into the three primary colors.
B Pickup Device
The pickup device takes light from a scene and translates it into electronic
signals. The first pickup devices used in cameras were camera tubes. The first
camera tube used in television was the iconoscope. Invented in the 1920s, it
needed a great deal of light to produce a signal, so it was impractical to use in a
low-light setting, such as an outdoor evening scene. The image-orthicon tube
and the vidicon tube were invented in the 1940s and were a vast improvement on
the iconoscope. They needed only about as much light to record a scene as human
eyes need to see. Instead of camera tubes, most modern cameras now use light-
sensitive integrated circuits (tiny, electronic devices) called charge-coupled
devices (CCDs).
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When recording television images, the pickup device replaces the function of film
used in making movies. In a camera tube pickup device, the front of the tube
contains a layer of photosensitive material called a target. In the image-orthicon
tube, the target material is photoemissive-that is, it emits electrons when it is
struck by light. In the vidicon camera tube, the target material is
photoconductive-that is, it conducts electricity when it is struck by light. In both
cases, the lens of a camera focuses light from a scene onto the front of the camera
tube, and this light causes changes in the target material. The light image is
transformed into an electronic image, which can then be read from the back of the
target by a beam of electrons (tiny, negatively charged particles)
.
The beam of electrons is produced by an electron gun at the back of the camera
tube. The beam is controlled by a system of electromagnets that make the beam
systematically scan the target material. Whenever the electron beam hits the
bright parts of the electronic image on the target material, the tube emits a high
voltage, and when the beam hits a dark part of the image, the tube emits a low
voltage. This varying voltage is the electronic television signal.
A charge-coupled device (CCD) can be much smaller than a camera tube and is
much more durable. As a result, cameras with CCDs are more compact and
portable than those using a camera tube. The image they create is less vulnerable
to distortion and is therefore clearer. In a CCD, the light from a scene strikes an
array of photodiodes arranged on a silicon chip. Photodiodes are devices that
conduct electricity when they are struck by light; they send this electricity to tiny
capacitors. The capacitors store the electrical charge, with the amount of charge
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stored depending on the strength of the light that struck the photodiode. The CCD
converts the incoming light from the scene into an electrical signal by releasing
the charges from the photodiodes in an order that follows the scanning pattern
that the receiver will follow in re-creating the image.
C Encoder
In color television, the signals from the three camera tubes or charge-coupled
devices are first amplified, then sent to the encoder before leaving the camera.
The encoder combines the three signals into a single electronic signal that
contains the brightness information of the colors (luminance). It then adds
another signal that contains the code used to combine the colors (color burst), and
the synchronization information used to direct the television receiver to follow
the same scanning pattern as the camera. The color television receiver uses the
color burst part of the signal to separate the three colors again.
IV SCANNING
Television cameras and television receivers use a procedure called scanning to
record visual images and re-create them on a television screen. The television
camera records an image, such as a scene in a television show, by breaking it up
into a series of lines and scanning over each line with the beam or beams of
electrons contained in the camera tube. The pattern is created in a CCD camera
by the array of photodiodes. One scan of an image produces one static picture,
like a single frame in a film. The camera must scan a scene many times per
second to record a continuous image. In the television receiver, another electron
beam-or set of electron beams, in the case of color television-uses the signals
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