What is the monitoring camera gamma correction

Gamma correction is to edit the gamma curve of an image to perform non-linear tone editing on the image. The dark part and the light part of the image signal are detected, and the ratio of the two is increased. Improves image contrast. The conversion curve of the output voltage and the corresponding brightness of the screen used in the computer graphics field is called the gamma curve. In terms of the characteristics of a traditional CRT (CathodeRayTube) screen, the curve is usually a power function, y=(X+e)Y where Y is the brightness, X is the output voltage, e is the compensation coefficient, and the power value (y ) For the gamma value, changing the magnitude of the exponent (y) can change the gamma curve of the CRT. The typical gamma value is 0.45, which makes the image brightness of the CRT linear. A monitor screen such as a television using a CRT's must be calibrated since it is an exponential function because the luminous gradation for the input signal is not a linear function.

In TVs and graphic monitors, the electron beam generated by the kinescope and the brightness of the resulting image do not change linearly with the input voltage of the kinescope. The electron flow changes according to the exponential curve compared to the input voltage, and the index of the transmitter voltage It is larger than the electron beam index. This shows that the dark area signal is darker than the actual situation, and the bright area is higher than the actual situation. Therefore, to reproduce the picture taken by the camera, the TV and the monitor must perform gamma compensation. This gamma correction can also be done by the camera. The purpose of gamma compensation for the entire television system is to make the camera output signal according to the symmetry between the brightness of the incident light and the brightness of the picture tube, so the response to the image signal introduces an opposite nonlinear distortion, ie the gamma curve with the television system. The corresponding camera gamma curve, its value should be 1/y, called the camera's gamma. The gamma of the TV system is about 2.2, so the camera's non-linear compensation gamma value is 0.45. The gamma value of the color picture tube is 2.8, and its image signal correction index should be I/2.8=0.35, but due to the influence of stray light inside and outside the picture tube, the contrast and saturation of the reproduced image are reduced, so the current color camera The gamma value is still more than 0.45. In practical applications, the gamma value can be adjusted within a certain range according to the actual situation to obtain the best effect.

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