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Pentax SMC DA 35mm f/2.8 Limited macro - Review / Test Report - Analysis |
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Lens Reviews -
Pentax
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Thursday, 21 August 2008 06:00 |
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Page 2 of 3
Distortions
The lens shows a slight degree of barrel distortion (0.4%) which is not overly field relevant.
Vignetting
Typical for many dedicated APS-C lens the vignetting is somewhat more pronounced. At f/2.8 you can expect a decrease in corner brightness of ~0.8EV which can be visible in critical scenes. The problem is very reduced at f/4 and pretty much negligible from f/5.6 onwards.
MTF (resolution)
The Pentax lens produced very good resolution figures in the MTF lab. The center performance is very high straight from f/2.8 whereas the border quality is somewhat reduced here (still good to very good). The peak performance is reached around f/5.6 with an excellent center quality and very good borders. As usual diffraction takes its toll at smaller aperture settings - if possible avoid f/22.
Below is a simplified summary of the formal findings. The chart shows in line widths per picture height (LW/PH)
which can be taken as a quantity for sharpness. If you want to know more about it you may check out the corresponding
Imatest Explanations.
Chromatic Aberrations (CAs)
Lateral chromatic aberrations (color shadows at harsh contrast transitions) are generally well
controlled below f/5.6 (<1px at the image borders) but the problem increases the further you stop
down. The CA level may be somewhat disturbing at f/22 but then that's no mainstream setting anyway.
Bokeh
The quality of the blur in out-of-focus areas is something of a mixed bag. At standard focus
distances the bokeh is somewhat prone to produce halos which can look rather nervous. This is slightly disappointing for this kind of lens.
The situation seems to improve in close-up situations although the more shallow depth-of-field does surely help here.
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