I recently bought a used roll film holder and found that a large number of shots were slightly out of focus, more than my normal quantity. I began looking at th e alignment of the film in relation to the groundglass and found some problems. I have an Omega45E camera, a Graphic roll film holder, a Toyo roll film holder, and a variety of cut sheet film holders.
I removed the back from the camera and using a straight edge layed across the fl ange that attaches to the camera I measured the distance to the ground glass, I' ll call this the reference distance. I made this measurement at several points a cross the glass. I then took cut film and roll film holders,loaded scrap film in to them, installed them in the back and measured the same way. The distance to t he film was between +.023 inches and -.005 inches of the reference measurement t o the ground glass. The Toyo roll holder was the worst at +.023.
This seems like a wide tolerance. The +.023 inches could explain the out of focu s shots, the problem was worse with close subjects with the in focus plane being farther from the camera than appeared in the ground glass. How do I go about fi xing this situation. I plan on doing more close up work over the winter months w here this problem will be exagerated. Are there better measurement methods that I should use to determine the extent of the problem? How do I fix them?
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