Define Gamma. Why is gamma correction done in the camera ? What is the value gamma for picture tube? Show that the video bandwidth is approximately 5 MHz.

Define Gamma. Why is gamma correction done in the camera ? What is the value
gamma for picture tube? Show that the video bandwidth is approximately 5 MHz.

Gamma : Video output of camera is not a linear function of the light input. Similarly the light output of the picture tube is also a non linear function of the electrical output. Thus the picture obtained at the output lacks the appearance of input in its entirety. The transfer is called the gamma of the system.

Gamma correction is done in Camera tube because there is non linear relationship between’ output current and light intensity both at the pick up tube and the output CRT in receiver. At the receiving end the light output is the square of the input video signal voltage. The effect of this is to compress the black and stretch the white. It is done with the help of black to white gray scale chart. Approximate value of gamma is 1.2.