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Forum: Pentax Lens Articles
04-19-2017, 12:52 AM
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This is my stardard lens for the K-5 and initially I wanted to use it with my K-1. But I only used it once or twice since I wasn't happy with it. It's simply an extreme DA-example with narrow image circle. In the end I bought the DFA28-105 instead. Similar feeling but great results - the right choice for me.
Seems to be similar to the DA55-300PLM. My observation for this lens classified by open aperture:
f/4.5: 55 - 63 - 70 - 78 - 88 - 98 - 108 -120 - 135 mm => dark corners up to dark image circle areas and back - very bad in the middle range, widely usable in FF Square mode, allows crops bigger than APSC area
f/5.6: 150 - 170 - 190 - 210 - 230 - 260 mm => FF compatible, existing corner vignetting can be mastered
f/6.3: 300 mm => dark corners, usable in FF Square mode, allows crops a little bit smaller than FF area
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Forum: Pentax Lens Articles
01-05-2016, 10:47 AM
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I made some images with the DA20-40 some time ago. Liked handling and image quality very much. Had it on my wishlist until I read that it doesn't cover the FF image circle. Can't find the post anymore - sorry. But I checked the PF Pentax Zoom List for both lenses.
Filter thread of FA20-35 = 58mm, DA20-40mm = 55mm. This may be the relevant indication for not being (fully) FF compatible.
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Forum: Pentax Lens Articles
01-05-2016, 08:04 AM
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I remember that in a thread it was said that it isn't. Would be interesting to see how much cropping of an FF image yield to usable results. Using the lens with the DA 1.4x TC we could get an FF compatible but slow f4-5.6/28-56mm combination.
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