Pentax SMC-FA 100mm f/2.8 macro - Review / Lab Test Report - Analysis
Lens Reviews -
Wednesday, 26 December 2007 01:39
Page 2 of 2
Macro lenses are designed to produce minimal distortion and the Pentax SMC FA 100mm f/2.8 macro
does certainly qualify here (0.02%).
The chart above has a real-world size of about 120x80cm.
As a full format lens the 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. From f/5.6 the problem is hardly detectable
The FA 100mm f/2.8 macro produced very high resolution figures in the MTF lab.
The resolution is already very good and exceptionally even at f/2.8. Stopping
down does only result in a marginal improvement although a slight peak is
reached at f/8 with an excellent center to border quality (just). Beyond f/8
the lens runs into the usual and unavoidable diffraction problems. At f/22 the
resolution is still amazingly high - actually too high in relation to the
diffraction problems at this setting. The nominial aperture (f/22) is probably
larger than the effective one. At f/32 there's only the typical image soup left.
The contrast level of the FA 100mm f/2.8 macro seems a bit lower compared to
other lenses in this lens class.
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
Chromatic Aberrations (CAs)
Lateral chromatic aberrations (color shadows at harsh contrast transitions) are
low and generally not field relevant at all tested settings.
The Pentax SMC-FA 100mm f/2.8 macro is an very good lens without significant
weaknesses. The resolution level is very high (although not exceedingly so) from
f/2.8 all the way down to f/22 (nominal, the effective aperture is probably larger).
Distortions are absent and CAs are not field-relevant. Same goes for vignetting.
Thanks to a metal body and tight tolerances the build quality of this old lens