The Olympus 14-42mm does well in our studio tests, sitting distinctly towards the top of the class. Indeed it's something of a talented all-rounder, doing pretty well in all tests and showing no obvious weak points.
|Sharpness||The lens delivers consistently good results at all focal lengths, and unlike most of its competitors even gives good results wide open at telephoto. Optimum performance (unsurprisingly) tends to be around F5.6-8, although it's not at all bad wide open either. There's a noticeable loss in sharpness due to diffraction at F11 and smaller apertures, but Olympus has sensibly limited the minimum aperture to F22 at all focal lengths.|
|Chromatic Aberration||Chromatic aberration is kept pretty well under control, and indeed overall is probably just about the lowest of any kit lens. The only negative is that CA is also visible wide open at the telephoto end, although here it disappears quickly on stopping down.|
|Falloff||We consider falloff to start becoming a potential problem when the corner illumination falls to more than 1 stop below the centre. Falloff is only likely to be an issue with this lens wide open at 14mm, and essentially disappears on stopping down to F6.3 (there's also slight falloff wide open at 18mm). The falloff pattern on the tested sample was noticeably decentred with respect to the sensor.|
|Distortion||As usual distortion is most pronounced at wideangle, with 1.4% barrel at 14mm. This progressively reduces at longer focal lengths, and becomes essentially imperceptible from 25mm to 42mm. Yet again, a perfectly acceptable performance.|
Somewhat unusually, we were able to run a complete set of tests on two different copies of this lens during the course of this review. We found that, whilst there were slight but measurable (and reproducible) differences in the shapes of the resolution curves across the frame, these were generally insignficant. Differences which might be noticeable in real-life shooting were limited to the widest aperture settings, where one lens performed slightly worse than the other at wideangle, but conversely a little better at the telephoto end; results at all focal lengths were equalised by stopping down to F8. The data presented in the widget above is from the (marginally) superior overall performer of these two lenses.
Lens axis offset angle
One issue we did observe during the course of these tests (and a reason for requesting a second sample) was that the lenses did not project an image of what was precisely in front of the camera, but instead apparently pointed off at a slight angle. The practical effect of this was that we had to move the camera slightly out of line with the centre of our test charts in order to obtain a symmetric image; and by measuring this displacement could determine an apparent ‘offset angle’. The effect is largest at the widest angle setting, so this is the figure we report.
It's not clear what causes this issue, but at a guess it may be related to Olympus's extensive use of ED glass in their designs, which is required to minimise aberrations with these short focal length, highly retrofocal designs (ED glass requires extremely precise alignment during lens construction, and deviations from the ideal during manufacture could conceivably give a 'tilt' effect). We also assume that it is likely to vary between samples of any individual lens; the numbers we report should therefore be taken as representative only of the sample(s) we have tested. It's also important to stress that this was only observable due to the critical alignments needed for shooting our test charts, and had no obvious effect on real-world shooting (you'd only see it when shooting alignment-critical applications such as copy work).
The measured lens axis offset angles at 14mm were 1.3° and 2.0° for the two samples tested; the lens with the smaller offset angle gave slightly better overall performance, most notably wide open at wideangle.
Specific image quality issues
As always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests. Overall this lens is an excellent performer, delivering consistently good results across a wide range of shooting situtions and rarely putting a foot wrong.
The 14-42mm shows excellent control of flare, especially if you make a habit of using the hood in difficult lighting conditions. It does well in both of our 'real-world' flare tests, with the sun in the corner of the frame at wideangle, or out of the frame but impinging directly on the front element at telephoto.
|14mm F8, sun in corner of frame||42mm F8, strong backlight|
Background blur ('bokeh')
One genuinely desirable, but difficult to measure aspect of a lens's performance is the ability to deliver smoothly blurred out-of-focus regions when trying to isolate a subject from the background, generally when using a long focal length and large aperture. Olympus make a selling point of their circular aperture design, and consider the rendition of blurred backgrounds to be 'one of the big advantages of this lens'.
On one level they are indeed correct; this lens can deliver quite attractive bokeh under the right conditions. The problem is simply in getting a blurred background in the first place; for any given angle of view and subject distance, background blur is dependant fundamentally on the physical diameter of the aperture, and at 42mm F5.6 that's just 7.5mm (in context, even a typical APS-C kit lens at 55mm F5.6 has an aperture of 9.8mm). In practice this gives the 14-42mm the least control over depth of field of any current standard zoom for DSLRs; this is fundamentally the price you pay for such a compact size.
The best results are generally obtained in macro shots, with the greatest relative separation between subject and background. At slightly longer subject distances, the lens can render specular highlights in a harsh-edged ring pattern, which isn't pretty (although to be fair, pretty typical for a kit lens).
|42mm F5.6, ISO400||50% crop, centre right of frame|
|42mm F5.6, ISO100||100% crop, centre left of frame|