I've recently been testing a Fujinon-C 300mm lens in 4x5 format. My test result s suggest this lens has some peculiar behavior which suprises me. I'd like to p ost what I've done, and get some feedback to understand if there are problems wi th my test methodology. I'd be interested in hearing other people's experience with this lens - in particular people who use it to shoot 8x10.
The test did not involve test charts, but was a subjective empirical test shooti ng the John Hancock Tower (I. M. Pei) in Boston at infinity. The building has s harp horizontal and vertical lines at every floor which allows direct comparison of sharpness as you go up in height. The camera was an Arca Swiss F (metric) s itting on a Arca Swiss B2 head with Gitzo 410 legs. I tilted the rail 15 degree s to keep both the front and rear standards as solid as possible and allow the r equired rise without having to reset the basic camera position. The ground glass and lens were set parallel to the building using an accurate external level. T he starting position (0 rise) was determined by placing a level between the tops of the standards. Film was Ilford FP4+ in a Grafmatic with good septums. F-s tops were between 22 and 22 +1/3. Shutter speed was 1/60. I developed the B&W negs in Rodinal 1:50.
I shot exposures at 0, 70, 100 and 130mm of rise. Since the Fujinon-C 300mm has an advertised image circle of 380mm, you need about 130mm of rise to see to the edge of this field. Examining the negs with both 7x and 10x loupes, I'd say th e zone of very-sharp focus falls within about a 230mm image circle. The negativ e without any rise is incredible - you couldn't ask for a sharper more contrasty image. By the time you reach an image circle of 260mm, there is no question th at the image has degraded significantly. Out at 380mm, there is an image, but t he sharpness resembles what a near-sighted person with 20-200 vision might see.
I'm guessing there must be some problem with my test. Please comment. Again, I 'm very interested in hearing from anyone with direct experience with this lens. Certainly anyone who shoots 8x10 with this lens could easily validate or quest ion my results.