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Studio Tests

The Lumix 7-14mm turns in an impressive performance in our studio tests. Distortion is being corrected in software, as is lateral chromatic aberration when used on Panasonic camera bodies (although not on the Olympus Pen series), and this is reflected in the corresponding results. Overall the lens is a very capable performer, particularly at the wider focal lengths; it's a little less good at 14mm although still quite respectable.

Compared to the tiny Olympus M ZD 9-18mm F4-5.6, there's really little in it. The Panasonic offers more consistent sharpness across the frame at 9mm, but the Olympus is noticeably sharper in the central region at 14mm; and when used on an Olympus camera such as the E-P2 the Panasonic shows a little less lateral chromatic aberration.

Sharpness
Towards the wide end of the zoom, central sharpness is excellent but there's a little deterioration towards the corner of the frame. Results hold up well on zooming longer, and while at 14mm sharpness drops noticeably, even here it's pretty good. Best results tend to be obtained in the F4-F8 range, with diffraction degrading the image progressively on stopping down further. In general we'd probably avoid apertures smaller than F11.
Chromatic Aberration
Chromatic aberration is auto-corrected to the point of invisibility on Panasonic bodies. However testing the lens on an Olympus camera shows its true colors; CA is visible at all focal lengths but is most pronounced at wideangle, where it's visible as green/magenta fringing towards the corner of the frame.
Falloff
We consider falloff to start becoming a potential problem when the corner illumination falls to more than 1 stop below the center. The 7-14mm shows noticeable falloff wide open throughout the zoom range, although it pretty much disappears in stopping down to F5.6.
Distortion
Distortion is being corrected in software, and is therefore pretty low. Our tests (slightly surprisingly) measure low levels of pincushion distortion through the entire range, which is worst at 14mm (-1.2%). This probably reflects a slight over-correction of distortion at the close distances used to for these particular chart tests; uncorrected data shows barrel distortion through much of the range (see below).

Macro Focus

Ultrawide zooms are never going to score highly for macro performance, and the 7-14mm doesn't buck the trend. The closest focus is 22.5cm (in manual focus), somewhat closer than the advertised 25cm. This gives a working distance of 12cm from the front of the lens to the subject.

The center of the frame is sharp wide open but the corners are noticeably soft. They sharpen up on stopping down, though, and the best results overall are obtained at about F11. Distortion is low and chromatic aberration almost invisible.

Macro - 188 x 141 mm coverage
Distortion: Slight pincushion
Corner softness: Low
Focal length: 14mm (28 mm equiv)

Software correction of lens aberrations

A fundamental component of the Micro Four Thirds system design is the use of software to correct certain lens aberrations, most notably geometric distortion. For most users this is completely transparent - the camera corrects both the viewfinder image 'on the fly' and the JPEG files it records. Also, the relevant correction parameters are encoded directly in the raw file, which means that both the software supplied with the camera and industry-standard alternatives (including Adobe Camera Raw and Capture One) will convert raw files correctly. However users who like to experiment with more obscure raw developers which are unable to apply the requisite corrections will find themselves with highly distorted images, especially when shooting at the widest angles.

Geometric Distortion

The graphic below shows just how much distortion you can expect to see when working with an unsupported converter. There's strong barrel distortion at wideangle which reduces progressively on zooming in, with the lens giving almost perfectly neutral results at 12mm before turning to pincushion distortion at 14mm. Clearly many images shot at the widest settings will benefit from correction - not only to render straight lines correctly, but also to match the original viewfinder composition. However it's worth pointing out that none of these distortion figures are much outside the range that we've previously seen from conventional SLR lenses, such as the Canon EF-S 18-200mm F3.5-5.6 IS (which ranges between extremes of 3.4% barrel at wideangle to -1.9% pincushion at 50mm).

7mm
(+ 3.4%)
8mm
(+ 2.5%)
9mm
(+ 1.7%)
10mm
(+ 1.0%)
12mm
(-0.3%)
14mm
(-1.2%)

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.

Flare

Control of flare is a critical feature of a super-wide lens; with such a broad view of the world, bright light sources will find themselves in the frame on a regular basis. This is especially the case with the 7-14mm, with that large domed front element making it potentially susceptible to stray light from all directions. Of course it's also important to keep the front of the lens scrupulously clean - fingerprints or big blobs of dust won't help its image quality at all.

With all this in mind, the lens does a remarkably good job of dealing with flare. It will give the expected multicolored spot patterns when the sun is placed in the frame, but they tend to be relatively unobtrusive. Oblique sidelight can be more problematic, and just occasionally will result in flare streaks across much of the frame (to be fair, though, we only encountered this in a tiny fraction of the images we shot, even in bright sunlight).

7mm F5.6 13mm F6.3, sidelight

Chromatic aberration

Wideangle zooms are bound to suffer from a degree of lateral chromatic aberration, and the 7-14mm F4 is no exception. When the lens is used on Panasonic bodies it's automatically corrected out in software, but on Olympus cameras this isn't the case and color fringing towards the corners of the frame is quite visible.

The samples below given an idea of how this looks in practice when examining camera JPEGs from the Olympus E-P2. Very strong fringing can be seen at the widest setting, however zoom in to 14mm and things improve. Of course lateral CA like this can be removed by many raw converters, and we've included examples from Adobe Camera Raw 5.7 to show how effective this kind of treatment can be.

7mm, Olympus E-P2 14mm, Olympus E-P2
F6.3, camera JPEG F6.3, camera JPEG
100% crop, top left 100% crop, lower left
CA correction in ACR 5.7* CA correction in ACR 5.7*

*Parameters used: -20 red/cyan, +50 blue/yellow at 7mm; -20 red/cyan, +20 blue/yellow at 14mm

7mm vs 9mm - how big is the difference?

Clearly the choice facing Micro Four Thirds users who wish to buy a wide zoom right now is between the Panasonic 7-14mm F4 and the Olympus M ZD 9-18mm F4-5.6, and the question many will be asking themselves is 'Do I really need the extra 2mm at the wide end?'. Because while it's easy enough to quote the figures - 114º angle of view vs 100º - visualizing the difference, and understanding its usefulness is less straightforward.

7mm
9mm

These examples demonstrate the difference in field of view between 7mm and 9mm, and clearly it's considerable (although whether either of these shots really benefits from the extra angle is open to question). In fact it's quite difficult to convey just how wide 7mm really is - often it seems like there's no subject, however large that you can't fit into the frame. But with that field of view come pitfalls - effective framing becomes increasingly challenging, and it's all too easy to end up with vast expanses of featureless foreground (exacerbated by the slightly 'tall' 4:3 aspect ratio of Micro Four Thirds).

This shot illustrates both the advantages and disadvantages of the 7mm wideangle. It allows the entirety of Admiralty Arch in London to be fitted into the frame, which is no mean feat; and by keeping the camera level, converging verticals have been avoided. But the empty foreground is distracting, and would need to be cropped out heavily to make an effective print.

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