Hello! Previously, I asked for help in constructing a hyperfocal 16x 20 camera. Assuming a CoC of 0.4mm, and f64, using the 28 inch front cell of an old Gundlach Rapid Rectilinear Convertible lens, the hyperfocal distance was 70 feet, with the near focusing distance of 35 feet. I plan on loading the camera with film/paper in the darkroom for single shot use, and use it for landscapes.
Today, I used a large cardboad box, and taped 8x10 VC paper to each corner, trying for the appropriate film plane of about 29 inches from the lens. I curved the film in the right upper quadrant and left it flat in the left lower quadrant. I exposed for 40 seconds, which appears to be overexposed about 1 to 2 f-stops after development.
Happily, I see no light falloff at the corners. The curved film plane didn't seem to do much with light fall off, since the edge was about 85% illuminated compared to the center at this focal distance, but I'll probably keep it in the final design, since it would help with the focus at the edges of the film (I think).
Anyway, the 28 inch cell of the Gundlach convertible seems to do the trick. I'll probably purchase an inexpensive shutter and attach it to the front of the lens cell, since at f64, exposure times may be too short to control accurately with a lens cap.
Best regards.
Mike
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