This subject was chosen due to its rectangular and symmetric nature which readily reveals lens distortion.
At least 10 minutes were spent leveling the camera as precisely as possible and ensuring left-to-right symmetry. This is rather difficult using a 2/3 frame camera with its small viewfinder, even using Nikon's “Type E” focusing screen, which contains extra grid lines. Even looking through the viewfinder at a slightly different angle changes the apparent coverage slightly. Alignment was very close, as good as could be achieved. A Photoshop rotation of -0.22 degrees levels the image horizontally, determined by using the center frame from the Schneider lens, and rotating until symmetry was achieved on the far right and far left of the center frame. The -0.22 degree rotation was confirmed as accurate using the center frame from the PC-Nikkor 28mm/f4.
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