K20 body or 31mm lens dilema

Started Jul 29, 2008 | Discussions thread
Marc Sabatella
Veteran MemberPosts: 6,677
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Re: K20 body or 31mm lens dilema - update
In reply to rcevans, Aug 7, 2008

rcevans wrote:

I'm reconsidering my dilema. I will need to research the IQ of a FA28
which is half the price of a FA31 and I believe quite a bit lighter.

There are several sites - some of which I think have been mentioned on this thread - that might prove useful, if you haven't checked them out yet.

For discussion/reviews of various older K-mount lenses, including most of the 28's:
http://stans-photography.info/

For the facts & stats on just about every Pentax product produced:
http://kmp.bdimitrov.de/

On that site you'll find summaries of some resolution tests; here is the data that was being summarized for the 28mm lenses:
http://www.takinami.com/yoshihiko/photo/lens_test/index.html

From Stan's site, I see that the FA28 is considered quite good, but not as sharp wide open at the K28/3.5. The screwmount version isn't discussed, but for some reaosn I was under the impression it was the same optically as the K-mount, except perhaps for SMC coating. Personally, I am finding the M28/2.8 (old version) to be very close in sharpness to the DA40, but it was considered only so-so by the folks quoted on Stan's site. On the other hand, apparently, the according to Yoshihiko's site, an issue with that lens seems to be the way resolution falls off considerably at the edges. So the crop factor may be making this a better lens for APS-C than it was for film. The real eye-opener on Yoshihiko's site are the results for the M28/2. Again, lots of falloff toward the edges, but man, that thing seems like it would be killer sharp through most of the field on APS-C. Unfortunately, the 31 is not tested.

From Dimitrov's site, you can see the FA28 is barely half the weight of the FA31.

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