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Forum: Pentax SLR Lens Discussion
01-20-2014, 11:27 AM
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Forum: Pentax SLR Lens Discussion
01-11-2014, 02:44 PM
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Forum: Pentax SLR Lens Discussion
01-09-2014, 08:25 AM
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It's neither of those.
Neither the muddiness of the kit lens,
nor the standard unexceptionable sharpness
of a workaday pro grade zoom lens.
It's classic Pentax, with the kind of special rendering
that is characteristic of the Limited lenses.
If that doesn't mean anything to you,
you're welcome to move on.
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Forum: Pentax SLR Lens Discussion
01-08-2014, 12:36 PM
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I would not regard that as a negative reflection on any zoom lens!
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Forum: Pentax SLR Lens Discussion
01-08-2014, 09:22 AM
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At this stage, I think there are three factors that may account for its poor showing in some reviews and user experiences:
1. Excessive sample variation and QC issues in the first batch of lenses shipped out.
2. Less than optimal focusing with PDAF.
3. Vignetting at the long end.
I picked up a copy recently that seems to have gone beyond the first issue,
but I have noticed variability in the PDAF focusing on a K-50, especially at the wide end, on low-contrast subjects,
and occasionally the vignetting shows up, although it's easily fixed in PP.
The rendering of the lens plays in the same league as my Zeiss and Voigtlaender primes.
Quite amazing for a zoom, and certainly justifying the price being asked for it, IMHO.
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Forum: Pentax SLR Lens Discussion
01-07-2014, 08:54 PM
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Right, you really have to crop the DA 20-40 to get the reach of that 50. :rolleyes:
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Forum: Pentax SLR Lens Discussion
01-06-2014, 09:40 AM
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Adam, thanks for getting this informative review out there for us.
However, I did find the review rather confusing in places. For example:
"the 20-40mm controls chromatic aberrations (also known as coma, or more commonly known as fringing) very well, even in areas with strong highlights. In the center of the frame, we weren't able to provoke any visible coma."
"Coma" usually refers to comet-shaped distortion of off-center highlights.
Chromatic aberrations come in two flavors, lateral and longitudinal.
Fringing is a generic term, but "purple fringing" is a third effect, still not properly understood.
The gist of the review seems to be that the lens is good at the wider end,
but poorer at the longer end. To this extent, the new lens follows the pattern
seen in its FA 20-35/2.8 predecessor.
The main criticism of the new lens seems to be corner sharpness at 40mm:
"Coma is prominent at apertures wider than F11, however, which reduces contrast and perceived image quality."
If the "coma" here means lateral chromatic aberrations, then that can be corrected in PP to some extent.
The test photos were "unedited 100% crops of the original JPEG file."
If they were taken without in-camera correction,
then there is scope for some improvement of the perceived weak 40mm corner performance.
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