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Pentax-02 Standard Zoom 5-15mm f/2.8-4.5 (Pentax Q) - Review / Lens Test - Analysis |
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Lens Reviews -
Pentax Q
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Page 2 of 3
Distortion
The Pentax Standard Zoom lens produces a fairly heavy amount of distortion. It is, as expected, most pronounced (extreme @ 4.8%) at 5mm and eases a little at 7mm (medium @ 2.3%). The degree fades further towards the long end and there is basically no distortion anymore at 15mm. The general characteristic is clearly weaker than in "comparable" SLR lenses but we've seen a similar behavior e.g. from micro-four-thirds lenses (based on non-corrected RAWs). This is probably a side effect of the miniaturization.
Note: The Pentax Q (camera) offers to correct theses problems automatically (menu option).
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Move the mouse cursor over the focal length text marks below to observe the respective distortion
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7mm |
15mm |
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Vignetting
The Pentax Q Standard Zoom lens is extremely well corrected with respect to light fall-off in the image corners. This aspect is nothing to worry about.
MTF (resolution)
As already mentioned in our previous Pentax Q lens test, the system suffers somewhat from its small sensor size. The pixel-level sharpness is not comparable to systems using a bigger sensor. Within its scope the Pentax Q lens does an excellent job though. It is fully usable at max. aperture already and the excellent peak is reached at f/4 (at 5mm and 7mm respectively). You can already observe that diffraction is limiting the performance at the tele end (@ f/4.5). There's a more pronounced quality penalty at f/5.6 and f/8 should be definitely avoided. This is no lens issue but simply a physical limitation (due to the small pixel size) so don't use the aperture settings that you're used to on your DSLR. Remember that f/4 is already equivalent to f/22 on a full format DSLR!
The performance decreases substantially at very close focus distances.
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 CAs (color shadows at hard contrast transitions towards the image borders) are well controlled at less than 0.8px on the average. This is not disturbing anymore from a field perspective.
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