I was in Berlin earlier this week and I stopped by the Museum Fur Photographie (which is really just about Newton). They had a display of his cameras and I was quite surprised that he did a lot of his outdoor work with 35mm cameras. There was a Plaubel Makina 67 and Hasselblad 500, which he used principally for studio work, but there were several 35mm SLRs. It appears that he first used Nikons and later Pentax LX before switching to Canon EOS cameras during the autofocus days.