I have been toying with the idea of picking up an old 1D. I can't remember the guy's name that I saw do this, but he had his 1D modified to use a PL mount instead of an EF mount. Something about the 1D body (being thicker I guess) allowed for the flange distances to work out. He then mounted a $35,000 17mm wide angle to it. That lens was huge and could just suck in photons. With that lens, he could expose the night sky in 1/3 second exposures what would take multiple seconds on my gear. He mounted the camera to the front of his boat floating down river using night vision goggles to see where he was going. The images were fantastic. I always wanted to do something crazy like that