I remember that when you use a camera for take a photography, camera is producing an image which gamma you should correct, the same for scanners, etc.. but when you want to control the reflection amount (not the color), you use a number, usually from 0.0 to 1.0. If you want define “regions” with different amounts in your textured object, you create a texture with this different parts with differente values, not with the eye, but with a photoshop/gimp color info. I mean, the range of the image for this purpose is from 0.0 to 1.0, not a brutal hdr range. So if we talk about this “reflection texture” in HSV, I believe the V (valor) should be from 0.0 to 1.0. H and S, the truth, I don’t know…
The parameter you cant remember is in the file node texture > attributes > Vray > Texture Input Gamma.