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Pentax SMC DA 18-55mm f/3.5-5.6 AL WR - Lab Test / Review - Analysis |
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Lens Reviews -
Pentax
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Page 2 of 2
Distortion
The DA 18-55mm WR has a fairly typical distortion characteristic with a very pronounced barrel distortion (~3%) at 18mm, quite negligible distortion in the middle range and only slight (1%) pincushion distortion at 55mm.
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Move the mouse cursor over the focal length text marks below to observe the respective distortions
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| 18mm |
28mm |
55mm |
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Vignetting
The Pentax lens produces a quite strong amount of light falloff at 18mm @ f/3.5 so it's advisable to stop down to tame the issue. The vignetting is a little more moderate at 28mm @ f/4 and not a big deal anymore at 55mm.
MTF (resolution)
The resolution characteristic is quite decent albeit not flawless. The center performance is very good to excellent at 18mm and the borders are pretty good from f/5.6 onwards. However, the corners are much softer at large apertures and they just make it across the "good" threshold at medium apertures. There's also quite a bit of field curvature at this setting so it is advisable to stop down in any case. The middle range is the sweet spot of the lens. The center resolution is still impressive but even the corners exceed very good level from f/8 onwards. There's only a slight performance penalty at 55mm primarily in the image center.
Please note that the MTF results are not directly comparable across the different systems!
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 Imatest Explanations
Chromatic Aberrations (CAs)
Lateral chromatic aberrations (color shadows at harsh contrast transitions) surprisingly well controlled with an average pixel width of ~1px at the image borders at 18mm and even less beyond. Very few standard zooms show such a moderate CA characteristic.
Verdict
The Pentax SMC DA 18-55mm f/3.5-5.6 AL WR is certainly one of the more desirable "kit" lenses - at least in terms of haptics. Unlike other lenses in its class it has a comparatively decent build quality and its weather protection clearly stands out from the rest of the gang. The conventional screw-driven AF and the rotating focus ring are a little dated though.
Performance-wise it is capable of delivering decent results although it's nothing to rave about either. The corner quality is a certain weakness at 18mm specifically at max. aperture and this is also amplified by a fairly strong field curvature here. Stopping down to f/8 is therefore advisable. That's also a good idea to reduce the amount of vignetting at this setting. The lens is pretty sharp in the middle range to upper range if you stop down just a little bit. Lateral CAs are very well controlled and better than usual. The very noticeable barrel distortion at 18mm and slight pincushion distortion at 55m are rather typical for such a kit zoom lens again. So to summarize, it's not an obvious choice but a viable one.
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