Video Tech. Info: What is GAMMA?

What is GAMMA?

Gamma is a numerical value that indicates the relationship between the input and the output signals of a camera/monitor, as illustrated in the graph below. Generally, the straighter the gamma curve becomes (y=1), the more natural the image appears to the human eye. Because monitors have a gamma curve with a value of 2.2, the camera is usually set up with a reverse 0.45 gamma so the resultant curve is close to a straight line. The lower area of the curve affects dark colors while the higher area determines the colors close to white. The middle area represents colors in-between. The GAMMA function mainly corrects the color of middle areas of the curve.



Sony video cameras offer a variety of convinient gamma functions. These are STEP GAMMA for defining the area of the curve that needs to be corrected, MASTER GAMMA which corrects the entire curve, and GAMMA tables (STD and FILM) which offer a set of present gamma values. For example, you can deepen colors by setting MASTER GAMMA to a + value, then correct specific colors areas using STEP GAMMA, and finally select FILM from the GAMMA tables, creating images with rich colors and unique depth. However, because colors can be over-emphasized depending on the setting, it is necessary to check the image on your video monitor as you use these functions.