Setting gamma in the OSD, for monitors with such settings, adjusts the monitor's gamma curve without upsetting contrast or shade range. Adjusting gamma in the GPU driver modifies the GPU's output instead and reduces shade range and contrast in the process. It isn't really the same at all but in this case it's the only option other than using an ICC profile (covered in my review). As Mark pointed out the different Splendid presets will also alter gamma alongside various other variables. However; none really give a particularly desirable gamma tracking unless you're after visibility over 'realism'.