Panasonic Lumix G Vario 14-45mm f/3.5-5.6 ASPH OIS - Review / Test Report - Analysis
Lens Reviews -
Sunday, 15 February 2009 15:00
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Micro-4/3 files - both RAW as well as JPEGs - are automatically corrected either in the camera (JPEG) or in RAW converters (like Silkypix or Adobe Camera RAW). Therefore we decided not provide any figures here because they would show next to no distortion. The worst amount of corrected distortion is less than 1.3% at 14mm.
That said it is possible to use e.g. DCRaw in order to have a look at the uncorrected data. Technically Lumix lens shows a very poor performance regarding distortion specifically at the wide-end of the zoom range here. At 14mm we've a whopping ~5.5% of barrel distortion and it's not really much better at 18mm (~4.1%). The situation eases significantly at 25mm (2.2%) and at 45mm there's only a negligible degree of distortion. As mentioned this will usually not be noticed by users though.
As mentioned in the previous chapter both JPEG as well as RAW files are mostly corrected for some kind of lens aberrations (defects) and this is also true for vignetting. However, the correction mechanism does not fully succeed here. At 14mm @ f/3.5 we still have a fairly high vignetting of more than 1EV - beyond it is a lesser problem and not overly field relevant anymore.
However, we'd also like to mentioned that the principal vignetting figures are much worse than that. At 14mm we measured an edge shading of ~2.32EV @ f/3.5 which is extreme. The problem is already very much reduced at f/5.6 but even at f/11 we've still an edge deterioration of 1EV. Technically the lens is clearly underdesigned here. However, 14mm is really the worst spot. At all other tested focal lengths the vignetting is not overly field relevant even at max. aperture.
The Lumix lens produced very respectable resolution figures in the MTF lab. The center performance is generally very good to excellent whereas border quality is on a good (wide) to very good (tele) level. The field curvature (of the focus field) is marginal.
You may notice the rather unusual shape of the MTF "curve". This is quite typical for smaller image sensors which run into diffraction problems much "earlier" than APS-C or even full-format sensors.
Below is a simplified summary of the formal findings. The chart shows 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 chromatic aberrations (color shadows at harsh contrast transitions) are also auto-corrected so there's nothing relevant to report here on paper.
However, when using non-standard RAW converters it's quite obvious that the problem is generally on a quite high level (1-2px) from 14mm to 25mm.
As mentioned in the introduction your G1 RAWs may not always be as RAW as they may appear - or to be precise: the RAW processing. The Panasonic G1 RAW files contains unprocessed image data (more or less) but neither Adobe ACR/DNG nor Silkypix will give you access to it - reads: distortions, vignetting and lateral CAs are pre-processed. Here's a comparison of Silkypix vs RawTherapee based on a 14mm f/8 image (move your mouse cursor across the image for the Silkypix variant):