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Pentax SMC-FA 50mm f/1.4 - Review / Lab Test Report - Analysis & Verdict |
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Lens Reviews -
Pentax
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Page 2 of 2
Distortion
Typical for standard/normal lenses the Pentax FA 50mm exhibits only a minor degree of
barrel distortion - nothing to worry about under field conditions.
The chart above has a real-world size of about 120x80cm.
Vignetting
Thanks to the sweet spot behavior on the K10D vignetting is very well controlled.
However, regarding its ultra-large aperture vignetting is still a little stronger
at ~0.71V at wide-open aperture - at times this may be visible in very critical scenes.
From f/2 and up the problem is negligible.
MTF (resolution)
Standard lenses are simple fellows that survived the tides of time without
major design updates during the last 25 years. Usually 50mm lenses tend to
be a little soft at wide-open aperture but they are usually as
good as it gets around f/5.6 and the FA 50mm f/1.4 performs in-line to these
expectations.
At f/1.4 the center resolution is good whereas the borders are somewhat soft.
The contrast level is also relatively low at this setting. At f/2 the center
improves to very good resolution figures whereas the border quality remain on
a relatively low level. At f/2.8 there's a substantial
gain in quality with an excellent center and very good borders. At f/4 the center
reaches an outstanding performance which will surely be hard to be matched during
future Pentax tests. The sweet spot is reached at around f/5.6 where both the center
and the borders are excellent. At f/8 diffraction starts to take its toll.
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
not a particularly strength of the Pentax. With a peak around 1.5x on the average
at the image borders the problem can and will be visible at times. As usual I
should mention that CAs can be usually reduced to a negligible degree via
imaging tool support.
Verdict
The Pentax SMC-FA 50mm f/1.4 is an oldie but a goodie. At medium apertures the
lens is capable to produce stellar resolution figures. Typical for such lenses
the results are a bit soft at f/1.4 and less so at f/2 but still usable. Distortions
and vignetting are very well controlled. Lateral CAs are a little on the high
side for a fix-focal. The build quality of the lens is just fine - same goes for
the AF performance. Regarding its very low price tag it remains a highly
recommended lens.
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