Mamiya RB67 Split Image Screen Focus Issue
I recently installed a split image focus screen on my Mamiya RB67. I was quite disappointed with the first pics I took using this screen, my subject was out of focus but the near background was in perfect focus. Picture 1 is one of the pics I had the problem with, an outside statue of Madonna at a local church. This focus screen is a vertical split image, unlike most split image screens which are horizontal split image, so I had to focus on a horizontal feature line. In pic 1 I focused on a small "knot" in the center of the robe, visible at the top left of the pic (the pic is a crop of the original image blown up to "pixel size" in PSE 11). I was careful to focus properly on the "knot" and adjusted the lens floating element to the correct distance, about 20-30'.
Picture 2, of some stonework on the side of a building, was taken the same day with the same lens and is in perfect focus. Subject distance here was about 8'. Again, a crop at "pixel size" in PSE 11.
Picture 3, same subject as picture 2, taken with my Canon EOS 20D at the same time, also a "pixel size" crop, for reference.
All three pics I took of the statue had the same focus issue. I did use two cable releases to flip the mirror up and paused a few seconds before tripping the shutter. I am fairly certain I was accurately focused on the statue, so what went wrong? Operator error (maybe I accidentally moved the focus knob after initially setting the focus)? The stonework was in perfect focus, why not the statue? All my pics with my old matte screen were properly focused, is some sort of focus alignment required when changing focus screens?