Please Note: This blog post is part of a series of five posts altogether.
The posts include: Part 1, Part 2, Part 3, Part 4 and Part 5.

You may use this mechanism to enhance blurred images. Overdoing its application leads, however, to distortions:

Gamma

Gamma increases or decreases the middle graylevels. In other words, you compensate the non-linear behavior of picture tubes: