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The image distortion produced by micro 4/3 images is auto-corrected either directly in the camera (JPEGs) or in most RAW-converters. The "exposed" distortion is therefore moderate especially for a standard kit lens. It ranges from a moderate (~0.9%) barrel distortion at 14mm to marginal (~0.54%) pincushion distortion at 42mm. This is nothing to worry about from a field perspective.
However, the non-corrected raw images show a pretty different situation with an extreme (~6,8%) barrel distortion at 14mm (a new record to date - in the negative sense unfortunately).
If you move your mouse cursor over the image you can switch to the corresponding non-corrected results.
The tiny lens has a fairly mediocre vignetting characteristic. At 14mm and f/3.5 the amount of vignetting is around ~1.4EV which will be easily noticeable in field images. Nevertheless, the situation improves significantly when stopping down and are just slightly noticeable from f/5.6 onwards. The same applies throughout the whole focal length with one exception as there is still slight vignetting at 42mm and f/5.6. However, it's no surprise that the non-corrected images show consistently worse results particularly at 14mm.
The following graphs compare the vignetting characteristic of auto- and non-corrected files between 14 and 42mm from open aperture to f/11.
The following images illustrate the above mentioned heavy vignetting at 45mm.
The resolution figures of the lens are very decent. At 14mm and 28mm it produces an excellent to very good center performance. The borders are generally on a good level but at 42mm there's a stronger drop in quality although you should still be able to get very good results here.
Below is a simplified summary of the formal findings. The chart shows line widths
per picture height (LW/PH) which can be taken as a measure for sharpness.
If you want to know more about the MTF50 figures you may check out the corresponding
Chromatic Aberrations (CAs)
Lateral chromatic aberrations (color shadows at harsh contrast transitions) are heavily auto-corrected specifically at 14mm where the non-corrected RAWs have CA peaks way beyond 2px at the image borders. As you may notice below the problem is very much reduced after the auto-correction.