Remove any shaddows, specular highlights etc etc from the photo using the clone tool (or whatever else you have)

Thne desaturate the image so its greayscale then I generally save it out as a .tif file

If you then use the original photo (after touching it up a bit as previous) you can then plug this into the colour for matching bump/colour nodes.

You might need to play about with the colouyr gain settings in maya to get it looking exactly how you want