Help regarding vision.GammaCorrector

I was using the in- built gamma corrector function of the matlab. But I'm not able able to understand what it actually does. I read the basics of gamma correction, looked into the help provided by matlab for the same ( http://www.mathworks.in/help/vision/ref/vision.gammacorrector-class.html ). I tried applying it on simple matrix like 2*2 matrix with all the elements equal to 4 so that I could understand something from the results but that was not helpful. So can please somebody help me out.