Panasonic DMC-G2 Review
Studio Tests - Lumix G Vario 14-42mm F3.5-5.6 OIS lens
With the G2 and G10 comes a new kit lens, which in terms of headline spec differs from its predecessor only in having a 3mm shorter telephoto end. But there are physical differences too, most notably the loss of the OIS switch on the side of the barrel (replaced by a firmware command in the camera), a noticeably smaller front element, and a substantially increased usage of plastics in the construction (including the mount). The zoom and focus rings feel a little less smooth and refined too.
The 14-42mm F3.5-5.6 gives decidedly mixed results in our studio tests. It's not terribly sharp at maximum aperture at any focal length, but stop down to F8 and things improve dramatically. Geometric distortion and lateral chromatic aberration are automatically corrected in software (as usual for Micro Four Thirds), giving excellent results in these areas. The wide-open softness means the 14-42mm suffers when compared to either the older Lumix G 14-45mm F3.5-5.6 OIS or Olympus's equivalent M ZD 14-42mm F3.5-5.6, and while it's a match for either once stopped down to more commonly-used apertures, overall it's a slightly disappointing replacement for what was one of the best kit lenses on the market.
|Sharpness||Sharpness results are very much a mixed bag. The 14-42mm tests poorly wide open at all focal lengths, with low contrast resulting in low MTF50 readings, but it improves dramatically when stopped down. At wideangle it's sharp in the center but somewhat soft in the extreme corners; zoom in and sharpness becomes more consistent across the frame. The best results are obtained in the middle of the zoom range (18-35mm) stopped down to around F8, at which point sharpness is impressively high for a kit zoom right across the frame.|
|Chromatic Aberration||Lateral chromatic aberration is being corrected in software, and is therefore to all intents and purposes negligible.|
|Falloff||We consider falloff to become perceptible when the corner illumination falls to more than 1 stop less than the center. There's about a stop of falloff wide open at 14mm, but this disappears rapidly on stopping down. All-in-all, nothing much to be concerned about.|
|Distortion||Geometric distortion is being corrected in software, and is therefore negligible across most of the image range. We can measure a little residual barrel distortion at wideangle and pincushion at telephoto, but it's sufficiently low that you're never likely to notice it.|
|Like it's predecessor the 14-42mm isn't the greatest macro lens in the world. Our measured minimum focus distance is 28 cm (in manual focus mode), giving a working distance of 15 cm from the front of the lens to the subject. Maximum magnification is essentially identical to the 14-45mm, at 0.18x.
Image quality isn't great with the aperture wide open at F5.6, being a little soft across the frame, but once again sharpness improves substantially on stopping down to F8, and the best results right across the frame are obtained at about F11. Distortion is minimal, and there's no visible chromatic aberration.
|Macro - 99 x 74 mm coverage
Distortion: Very low
Corner softness: low
Focal length: 42mm (84mm equivalent)
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 wideangle.
The graphic below shows just how much distortion you can expect to see when working with an unsupported converter. We converted the raw shots from our distortion test using dcraw, which does not apply any corrections. It's fair to say that images shot at 14mm would require correction on most cases, not only to render straight lines correctly, but also to match the original viewfinder composition. However by 18mm distortion has fallen significantly, and correction would be necessary only in specific cases. At focal lengths of 25mm and longer, no corrections would be necessary.
Lateral chromatic aberration
The studio test data also clearly shows that lateral chromatic aberration is being corrected in the ACR-converted raw files (out-of-camera JPEGs are the same). The practical upshot of this is that the camera produces images which are essentially free of the color fringing which is normally visible with this type of lens, most obviously towards the corners of the frame. However Olympus cameras don't replicate this processing, so if you choose to use the Panasonic 14-42mm on a Pen body, fringing will be visible.
Again we've used dcraw to process our studio test shots in order to reveal the lens's underlying characteristics, and illustrated the fringing visually using the top left checkerboard pattern from our lens test chart. Note that, for the sake of clarity, where necessary we're using images corrected for barrel distortion in this comparison (using Adobe Photoshop CS4's 'Lens Correction' filter, with parameters of +7.7 at 14mm and +2 at 18mm).
What should be apparent here is that, even when uncorrected, chromatic aberration is relatively low; there's a little green/magenta fringing visible at 14mm, which progressively diminishes on zooming in, and effectively becomes invisible by 35mm. In normal shooting, though, it shouldn't really be a problem.
Change in angle of view on focusing
The 14-42mm, as is typical for internal-focusing zooms, gets noticeably wider on focusing closer (much like its predecessor, the 14-45mm).
Optical Image Stabilization
The 14-42mm follows Panasonic's usual approach of using lens-based optical image stabilization (OIS for short). Unlike Panasonic's other lenses, it forgoes a physical IS switch in favor of a firmware command in the camera, which simply adds 'Off' as an option to the IS mode menu (owners of older G-series cameras will need to update to the latest firmware to gain this choice).
We've generally found in-lens stabilization units to be pretty effective in real-world use, and to quantify this, we subjected the 14-42mm to our studio image stabilization test at a focal length of 42mm, using the DMC-G10 as the test camera. The subject distance for these tests was approximately 2m, and we used IS Mode 1 (always on), which we've generally found to be most effective.
We take 10 shots at each shutter speed and visually rate them for sharpness. Shots considered 'sharp' have no visible blur at the pixel level, and are therefore suitable for viewing or printing at the largest sizes, whereas files with 'mild blur' are only slightly soft, and entirely usable for less critical applications.
|42mm OIS OFF||42mm OIS ON (Mode 1)|
As we've come to expect, the OIS system performs pretty well in our tests, giving a substantial benefit for hand-held shooting. It does seem to take a little while to settle down, though, which isn't as easy to judge in an electronic finder as an optical one. It's therefore well worth taking multiple shots whenever your shutter speeds drop, to maximise your chances of success.
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