To make matters more interesting the actual gamma curve you should be using should be the one corresponding the the display you use to view the image. Very freq

To make matters more interesting the actual gamma curve you should be using should be the one corresponding the the display you use to view the image. Very frequently this isn't sRGB or anything close to it (pure power gamma curves are relatively common, if you're lucky the gamma is somewhere close to 2.4). It is in fact not even rare to encode an image with a gamma curve that's intentionally different from the display that's supposed to be used to view it, in order to, for example, prevent crushing black details or to avoid numerical problems (both reasons for the linear component in sRGB).