A while back, I made a post showing a free utility available for mac that was very comprehensive in calibrating a LCD screen. You can view that here. However, it was only available for Mac, QuickGamma is the nearest substitute for the estranged Windows users. I have not personally had a chance to test this one out because I am a mac fanboy but it looks well constructed and has some decent reviews around the blogosphere. View it here.
The relationship between the input signal and the luminance of a monitor is not linear but exponential with gamma being the exponent. Monitor gamma values usually range between 1.4 and 3.2. Because only a gamma value of 1 resembles a linear relationship, a gamma correction is necessary to achieve maximum reproduction quality. A monitor gamma value of 2.2 has become the de facto standard for Windows, the Internet and the digital photography. Under Windows a gamma correction is already automatically applied. This yields a linear luminance distribution for monitors with a real gamma of 2.2. Because most computer monitors do not have a real gamma of 2.2 an additional correction is required. With QuickGamma you can calibrate your monitor to a gamma value of 2.2 which in conjunction with the automatic gamma correction yields a linear luminance distribution for every monitor. More information and detailed instructions on how to use QuickGamma are available by pushing the Help button in QuickGamma.
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