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Samyang has some major optical obstacles to overcome, outside of the mechanical tolerances of the TS mechanism. The big problem comes from making essentially a medium format lens based on large image circle, fit into the much shorter flange distance of the 35mm-style body. This requires some amazing squeezing via retro-focus design, which typically introduces extreme curvature of field (round focal "plane") and light fall-off, among other possible aberrations such as CA, not to mention the obvious need for nearly pure rectilinear perspective. It's amazing Canon has pulled it off so well, but then again, they've been refining this sort of design for over 40 years. Can Samyang hit the ground running and match Canon's experience, or even come close? Odds are they can't. But it is a horse race, so who knows until the nag crosses the finish line.