HOW TO ADJUST YOUR  MONITOR
(Brightness & Contrast Controls)

Gray Scale

You should see all ten bars with a linear increase in contrast.
 

Gamma Scale

Step back from your monitor and the number you see in the in the block that blends
with the background is your gamma setting. Most Web photographers use 1.8.
Adjust your brightness and contrast for optimum setting.

Go to the source of this page: http://zonezero.com/calibration/english.html

Gamma Correction Explained:  http://www.cgsd.com/papers/gamma_intro.html