Olympus M.Zuiko Digital 14-42mm f/3.5-5.6 ED Review / Test Report - Analysis
Lens Reviews -
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Micro 4/3 JPEGs as well as RAWs converted via standard RAW converters such as Photoshop apply an auto-correction of distortions so we are not providing any charts here at this stage. The corrected images have a max. distortion of about 1.7% at 14mm, less so at other focal lengths. From a user perspective this is certainly a very decent performance.
However, when using DCRaw to convert the camera RAWs you can actually get access to the uncorrected RAW file. We measured a whopping 4.6% of barrel distortions at 14mm which is very extreme. The Panasonic 14-45mm f/3.5-5.6 OIS does still top this value though.
The vignetting figures are surprising - not only for you I suppose but also for us. There's virtually no edge shading! You may argue that this aspect is also auto-corrected but it's actually not - even the uncorrected RAWs are clean here. This is probably a side effect of the special (retractable) construction of this lens.
The resolution figures of the M.Zuiko are very decent. At 14mm and 25mm it produces an excellent center performance. The borders are generally on a very good level till about f/8. At 42mm there's a stronger drop in quality although you should still be able to get very good results here.
Please note that four-thirds cameras have a different diffraction characteristic than APS-C or full format cameras. The real-world sweet spot, the point of highest resolution, is generally around f/4. Therefore it's hardly possible to improve the performance by stopping down when using (such) slow speed lenses. Remember that f/8 on a four-thirds camera is comparable to f/16 on a full format camera.
Below is a simplified summary of the formal findings. The chart shows in 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 CAs (color shadows at the image borders) are well controlled at around 1px on the average at the image borders.
Unlike the Panasonic kit lenses the CAs don't seem to be corrected neither by the camera nor by e.g. Photoshop. This is somewhat surprising because this is actually an easy and very desirable correction aspect.