I never hear of having to gamma correct any camera/scanner images ever. If u use 8/16 bit images and they have imbeded gamma 2.2 u HAVE to use gamma corection. Unless those images DONT have gamma imbeded. It dont matter if u use it for reflection bump normal or what ever else you have. HSV is 0-1 or 0-255. HSV = RGB in basic just different control of attributes.
HSV
H = hue
S = saturation
V = value (brightness)