Olympus M.Zuiko Digital 12-40 mm f/2.8 ED PRO review - Distortion

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Olympus M.Zuiko Digital 12-40 mm f/2.8 ED PRO

18 December 2013

Arkadiusz Olech

6. Distortion

As long as you work with JPEG files or you develop the RAW files using the software provided by the producer, the distortion won’t be such a big problem. At 12 mm focal length you get slight barrel distortion, amounting to –1.02%. At higher focal lengths the problems are even less noticeable because at 25 mm the distortion level is –0.13% and at 40 mm it decreases to just –0.05%.

As our test concerns the performance of the lens itself we also checked how the optics dealt with distortion without any help; we did it by developing RAW files with the dcraw program which doesn’t correct automatically the geometric flaws of the lens. In that case, at the wide angle, you have to take into account a huge level of barrel distortion, reaching a level of –6.32%. For comparison, at the same focal length the Panasonic 12-35 mm f/2.8 got –6.54%, a tad higher result than that of the Olympus. With the increase of the focal length the distortion decreases: at 14 mm it still remains high, amounting to –5.11%, and at 25 mm it reaches just –0.60%. At higher focal lengths there is a sign change and at 40 mm you already see pincushion distortion of 0.80%.

It is an interesting fact that the Olympus, featuring a wider focal range that the Panasonic 12-35 mm, has better distortion results almost across the range. Unfortunately, though, it is clear the constructors didn’t even try to control distortion effectively, ceding that task completely to the software. We definitely don’t like such an approach because correcting such a high distortion level entails significant cropping of images.

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