The relationship between the input signal and the luminance of a monitor is not linear but exponential with gamma being the exponent. A gamma value of 2.2 has become the de facto standard in Windows, the Internet and the digital photography. This means that only monitors with a gamma value of 2.2 will produce a correct output. Despite the fact that the gamma values of monitors have improved over the years, many monitors still have a gamma value that deviates more or less from 2.2. A correction is therefore required to achieve optimal results. The monitor gamma can easily be corrected to 2.2 using QuickGamma.
http://quickgamma.de/indexen.html