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Pentax SMC-D FA 100mm f/2.8 macro - Review / Test Report - Analysis |
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Lens Reviews -
Pentax
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Page 2 of 3
Distortion
Macro lenses are designed to produce minimal distortion and the Pentax SMC-D FA 100mm f/2.8 macro
is no exception to the rule (~0.03%).
The chart above has a real-world size of about 120x80cm.
Vignetting
As a full format lens the D FA 100mm f/2.8 enjoys a sweet spot advantage on the K10D.
At f/2.8 the problem is slightly more pronounced but even here the level of vignetting
shouldn't be really field-relevant.
MTF (resolution)
The DFA 100mm f/2.8 macro produced very high resolution figures in the MTF lab but
it isn't necessarily a step forward compared to its predecessor.
At f/2.8 the resolution is very good (just) and very even. Stopping
down provides a extra kick till reaching excellent quality levels at f/5.6.
From f/8 the resolution figures are heading southbound again due to diffraction effects -
this is a physical limitation. The lens is capable to maintain a high quality
level till about f/16. f/22 should be generally avoided, more so f/32 which is also possible.
Interestingly the contrast level of the DFA 100mm f/2.8 macro seems obviously higher
compared to the old FA 100mm f/2.8 macro.
Please note that this test has been performed at a conventional working distance (~6m).
Dedicated macro tests are NOT possible at this stage!
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
relatively low and not overly field relevant at all tested settings. In extreme
contrast situations you may spot slight traces of purple fringing at f/2.8.
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