whilst rendering for most of the scenes i wanted the arm to appear as floating in dead space, the all the HDRI images I had to render realistically posed the problem of reflecting in the arm, for example on the chrome parts you could see the street from the HDRI image. This wouldn’t really give the impression of the arm floating in the void, so I created my own HDRI images in Photoshop, i experimented with a few until i got some nice clear reflections of white on my arm. images below show the different reflections cast, I changed the levels in Photoshop to get a better idea of the reflective shapes cast.
I couldnt quite seem to get a realistic look from these basic images about so I thought that mixing them with other images might work and it paid off, I used clouds as an over lay and adjusted the levels n curves in photoshop to finally get a look a wanted. Its a pretty cowboy approach and looks a mess but It worked out for me.