My experiment with using my DSLR as a digital back on my 4x5. Camera is the Arca-Swiss Discovery. Like all Arca-Swiss cameras this is completely modular. Meaning I was able to take off ground glass and replace with a flat 171mm lensboard. I epoxied an extension tube on the board and was able to then mount my Canon DSLR. Focus is accomplished by use of live view on the camera. I can employ tilt and shift. See more on the experiment on my Large Format Camera Blog thelargeformatcamera.blogspot.com/