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Pentax SMC-DA 50-200mm f/4-5.6 ED - Review / Test Report - Analysis |
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Lens Reviews -
Pentax
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Page 2 of 3
Distortion
The DA 50-200mm exhibits only a slight degree of distortion throughout the zoom range.
Rather typical for such lenses there is slight barrel distortion (~1.2%) at the wide
end (50mm) and slight pincushion distortion at 100mm and 200mm.
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Move the mouse cursor over the focal length text marks below to observe the respective distortion
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| 50mm |
100mm |
200mm |
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The chart above has a real-world size of about 120x80cm.
Vignetting
Typical for most dedicated APS-C lenses vignetting is quite pronounced
at wide-open aperture and the problem can be visible at times (~1EV).
It is no longer field relevant from about f/8 onwards.
MTF (resolution)
The resolution characteristic of the Pentax is highly varying and not
convincing. At 50mm the center performance is very good to even excellent
(f/8) but the border quality is dismal at wide-open aperture and not much
better by f/5.6. From about f/8 the resolution is good. Usually I also provide
the extreme border performance for the widest zoom setting but I spare
you that (...). At 135mm the situation is quite a bit better with generally
good to very good results. However, there's a performance drop at 200mm
specifically at f/5.6. The center performance is good here whereas the borders
are soft again. The situation improves at f/8 and more so at f/11.
Please note that the 1st tested lens has been replaced by Pentax and the
2nd tested lens has been reconfirmed by Pentax to be within specs.
If you find all this to be surprising please feel free counter-check the findings
with the real world sample images provided below (e.g. the "castle" or the "wall"
image).
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) are quite
well controlled at 135mm and also 200mm. At 50mm the CAs are a little more
pronounced although still on an acceptable level.
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