Toronto. In the late 1960s I was in Montreal and devised a means to test lens resolution and shutter accuracy. It was during the shutter test that I realized my Exakta had a serious problem. It turned out a brass stop was nearly chopped off and a dry axel made a curtain erratic as it moved across the exposed film frame.
For the lens tests, I used a commercial lens testing poster and moved the tripod back and forth to get most of the chart in the frame for each focal length. For the Exakta, the Steinheil 135mm f/2.8 was by far the best of the three lenses in flatness of field and resolution. The Angenieux 28mm f/3.5 was terrible and the 55mm f/1.9 Steinheil not much better. Both lenses used a retrofocus design. However; in practice, both gave a reasonably sharp result although curvature of field shows deteriorated corner resolution in my tests.
George Dunbar found the above novel lens test in LIFE magazine. The photographer, Gene Smith, was using a much larger camera and elected to photograph hand written letters and words scattered over the image frame and at various distances. Check out LIFE for September 10, 1956 (pp16, 17).
You may wonder why we are using LIFE ads. There are a bunch of reasons: The magazine is no longer published; Google Books elected to scan and post every page of each weekly issue; LIFE was widely distributed and its name easily recognized; the magazine offers a slice of middle American life over a half century ago and by osmosis how we were in post war Canada at the time as we moved from Britain and its products to the brash outspoken America and American products.