This page shows results and examples from 50mm lenses. The 21-megapixel Canon EOS 1Ds Mark III was used to allow the maximum number of lenses to be tested, including Olympus and Nikon.
The amount of focus shift varies by lens. These examples were shot at a distance of 42 inches (1.07 meter). This is a distance that frames a head-and-shoulders portrait, which means that focus shift has the potential to throw the eyes into blur if focusing wide open (f/1.2 or f/1.4) and shooting in the f/2 - f/4 range. In short, it’s not an academic issue at all, but a very real challenge if shooting in this distance range.
In addition to the ~1m tests of the test target, tests were also conducted at the ~6 meter range. Test results showed improvement of detail and contrast at the focus target, indicating that any focus shift was more than compensated for by depth of field gained by stopping down. In addition front/rear sharpness both improved. In short, at the ~6m mark, none of the lenses appear to have a focus shift issue as a practical matter. Further tests could be done, focusing at various apertures, but the results were judged to not warrant it.
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Focused at f/1.4: mouse over for f/2.8 (actual pixels)