adopted in all television systems is rectangular with width/height ratio, i.e., aspect ratio = 4/3. There are many
reasons for this choice. In human affairs most of the motion occurs in the horizontal
plane and so a larger width is desirable.
can view with more ease and comfort when the width of a picture is more than
its height. The usage of rectangular frame in motion pictures with a
width/height ratio of 4/3 is another important reason for adopting this shape
and aspect ratio.
enables direct television transmission of film programmes without wastage of
any film area.
It is not
necessary that the size of the picture produced on the receiver screen be same
as that being televised but it is essential that the aspect ratio of the two be
same, otherwise the scene details would look too thin or too wide.
achieved by setting the magnitudes of the current in the deflection coils to
correct values, both at the TV camera and receiving picture tube.
important requirement is that the same coordinates should be scanned at any
instant both by the camera tube beam and the picture tube beam in the receiver.
Synchronizing pulses are transmitted along with the picture information to
achieve exact congruence between transmitter and receiver scanning systems.