Film holders are the first part of the solution. The catch is that the film is held at a different distance from the ground glass than the old glass plates were, so focus will be affected. I have an old Seneca plate camera on which the previous owner had flipped the ground glass around to frosted-side-out. While not an exact fix, it puts the point of focus closer to where it should be. I find I can make pretty darned sharp negatives for a hundred-year-old camera with an inexpensive original rapid rectilinear lens.
Another fix I saw on the large format forum is to cut a piece of aluminum with a rectangular hole in it the same size and position as the film window on the holder. The aluminum is the same thickness as negative glass (you'll have to do some research here.) The person posting the solution focused with the aluminum sheet in place, pulled it out, inserted the filmholder and made the image.
You also can fool with shimming the ground glass until you find the right focal point.
Good luck. I own two 100-plus year-old cameras and enjoy working with them.
Peter Gomena
