This lens turns in a very impressive performance across all categories in our studio tests. It's best in the wideangle to normal range, but still very good indeed at telephoto; perhaps the only real negative point is strong and complex distortion at wideangle.
|Sharpness||The lens performs best towards the wide end, although it's no slouch at telephoto either. In the middle of its range (around 18 to 25mm) it's impressively sharp right across the frame at normal working apertures. Optimum apertures are around F4-F5.6 at wideangle, and F5.6-8 at telephoto, but performance wide open is also very good. As expected with the Four Thirds format, diffraction starts to degrade the image quality at apertures of F11 and smaller.|
|Chromatic Aberration||Chromatic Aberration is most visible at the extremes of the zoom range, and almost nonexistent around 25-35mm. However even at 12mm and 60mm CA is not excessive, and the relatively linear shape of the curves suggests it should be easy to remove in software if required.|
|Falloff||We consider falloff to be a potential problem when the corner illumination falls to a stop or more lower than the centre. We measure just over a stop of falloff wide open at 12mm, which disappears on stopping down to F4 - aside from that falloff is not an issue. An excellent performance here.|
|Distortion||Barrel distortion is visible at 12mm, and shows an unusually strong 'wave' character with re-correction towards the corners of the frame. The rest of the range exhibits pincushion distortion, which is never excessively strong, peaking at 25mm and -0.78%. Overall very impressive considering the zoom range.|
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 one lens measured as being slightly softer than the other towards the telephoto end, but the difference was not observable in real-life shooting. The data presented in the widget is from the better performer of the 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 minimize aberrations on 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 somewhat 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 12mm were approximately 1.3° and 0.9° for the two samples tested.
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. This turned out to be a near-futile exercise with this lens, as it performed to a consistently high quality even in the face of some difficult lighting conditions, and proved to be extremely difficult to stress in any way.
The 12-60mm performed pretty well in our 'real-world' flare tests, doing well both with the sun in the corner of the frame at wideangle, and with the sun out of frame but impinging directly onto the front element towards the telephoto end. About the nearest we came to a glitch in the lens's performance was some striking multicoloured flare at 12mm when stopped right down to F16; but this was scarcely visible at more normal working apertures around F4-8.
|12mm F16, sun in corner of frame||70mm F9, 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. With its 60mm F4 telephoto end this lens is reasonably capable of giving a good degree of background blur, and can generate some pleasingly smooth bokeh given sufficient separation between the subject and background. It's less happy in macro situations with a relatively close background, where out of focus regions can become quite 'busy' in appearance with harsh-edged highlights. There's nothing particularly unusual here from a standard zoom lens though.
|60mm F4||100% crop|
|60mm F4||100% crop|
Not a criticism of this lens at all, but instead a pointer to one if its most interesting characteristics; with its minimum focusing distance of less than 25 cm across the entire zoom range, this lens has a superb macro performance for an internal-focusing zoom. Clearly it won't be as good as a dedicated macro such as the stellar 50mm F2.0, but the 12-60mm allows you to get some interesting close-up perspectives at the wideangle end, as well as more 'classic' macros at telephoto. The main problem (aside from the perennial issue of depth of field) is actually lighting the subject, which can be as little as 4cm from the front element.
|12mm F8||60mm F5.6|