Samsung NX 20 mm f/2.8 review - Distortion

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Samsung NX 20 mm f/2.8

16 January 2013

Arkadiusz Olech

6. Distortion

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When it comes to the distortion, Samsung unfortunately follows more and more fashionable strategy nowadays, leaving the distortion correction to the camera’s software and not correcting it by the optics of the lens. Regrettably when the distortion is really high there are a lot of problems. First a given lens has to feature a wider field of view than it is stated in the specifications. It is done so after the distortion correction and cropping the field of view the resulting field remains exactly as big as given in the specifications. The second problem is ‘pixel pumping’. If you use JPEG files or develop RAW files with the software delivered by the producer they always have a resolution of 14 Mpix, no matter what lens. However the higher the distortion the more you have to crop the image so less pixels take an active role in image registering. In extreme cases, when a lens has a really high distortion level, the resulting RAW or JPEG files can consist of even several millions of pixels full of nothing…Those void pixels are one problem, the other is the fact that such a RAW file is hardly ‘raw’ anymore because its resolution has been interpolated from a lower value…

When you look at JPEG files there is simply no distortion at all, everything corrected in a perfect way. The official result we got amounted to 0.07% so, within the margin of error, it equals to zero. The results on RAW files, developed by dcraw program are completely different, though, Here the barrel distortion is distinctly visible and its value we assessed as –4.30%. Taking into account the angle of view of this lens it is a weak result. It’s enough to say that full frame 28 mm lenses, with a slightly wider angle than the Samsung, tested here, have distortion ranging from –1% to –2%.