Pentax SMC-D FA 100mm f/2.8 macro - Review / Test Report - Analysis
Lens Reviews - Pentax

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!

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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