I have been making wood cameras for wet-plate and daguerreotype photography. In this, I make the plate-holders myself. So, the ground glass is of course the same distance (registration) from the lens as the plate when holder is inserted. ...... I am considering getting into making large format film cameras on a small scale. Here is my delima. Are all film holders made with the same proportion in regards to distance from film to edge of holder. All view cameras obviously come with a ground glass on it; but if the holder by S&S and Toyo or different distances, then it would throw off the distance the ground glass needs to be. OR. do you guys use a shim or something to correct this distance. Am I making any sense?? How do you check/correct the registration when using different film holders? I have always made my own cameras for collodion, so I don't have any experience with film cameras.