Gamma is the non-linearity in the CRT which matches closely the non-linearity in the human eye. It is no wonder that all display devices now artificially embed the non- linearity in the display. For example, a DLP (digital light processing) display that is a linear display emulates the non-linearity of the CRT.

In this image I take advantage of the non- linearity in a typical display which follows the 2.5 law of the CRTs.

This image is locally all gray (0.5) but I create a gradation by locally distributing the channels to create the color. If you want to go technical here is an article on wikipedia (hint: I use basically the same technique that they use in the test chart) or better still another one on gamma correction by the color guru Charles Poynton.

What is really interesting about this image is that even if you blur it a little bit, the image disappears. So the second image is the same image as the first and blurred with a gaussian blur with a radius of 2 pixels.

Note that if you may have to download this image and display it 1 to 1 to truly appreciate this effect. This image has a resolution of 864x1145.