In the late 90's and early 2000's Yoshihiko Takinami was well known on the Pentax Discuss Mailing List as an authority on the various iterations of Pentax lenses, and for accumulating several copies of each lens and testing them in a controlled fashion against each other, posting the results and declaring his rnarking of the lenses. You can Google to find his postings, some of which still are available today. The following is a summary discussion of the merits of the 28mm K-mount Pentax lenses posted to PDML between 1999 and 2004. The compilation of those postings is available on
Stan's Pentax Photography, and is useful still today for information on lenses up to introduction of the FA43/1.9.
I have kept the K28/3.5 and would only replace it with the K28/2 (if I ever had the chance). My M28/3.5 was very close to the K but I've always enjoyed the aesthetics of K lenses better than M or A.
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Yoshihiko Takinami replies:
F28/2.8 is optically identical to M28/2.8 (later model) and A28/2.8, if I remember correctly.
FA28/2.8AL was newly designed when FA lenses were introduced. FA28/2.8AL is a bit soft at wide open, and slightly soft at f/4, while K28/3.5 is very sharp even at wide open.
My personal ranking for Pentax 28m lenses are follows;
K28/3.5, K28/2 >= M28/3.5 >= FA28/2.8AL >>> M28/2.8 (old) >M28/2.8 (later), A28/2.8, F28/2.8
So F28/2.8 is never comparable to FA28/2.8AL in point of optical performance.
Yoshihiko Takinami [again] - I have something to add.
Try Hama rectangular hood (52mm) for this lens. It seems the best hood for K28/3.5 I have ever seen. It also works well with K24/2.8, K28/2, K30/2.8, K35/2, and K35/3.5 in my experiences.
[and in respose to another query . . .]
> I'm out looking for a cheap but good mf (28 or wider) wideangle lens. > I was thinking maybe one you have a good lens that you are willing to > give up, or maybe you couldjust give me a tip about what lens I should > buy. Go for a used K28/3.5 (SMC PENTAX 28mm f/3.5), a cheap but optically excellent lens, IMO. It is the sharpest 28mm lens that Pentax ever made. Or go for a used M28/3.5 (smc PENTAX-M 28mm f/3.5), a cheap but good lens, IMHO.
[and in response to yet another query . . .]
First of all, please note that a resolution test is a resolution test. It only shows a part of the optical performance of the lens tested.
As for the K-mount 28mm lenses of Pentax, I have/had experiences with K28/2, K28/3.5, M28/2, M28/2.8, M28/3.5, and FA28/2.8AL. I have resolution test results of K28/3.5, M28/3.5, and FA28/2.8AL among them.
I had been disappointed in the performances of M28/2 and M28/2.8 comparing then to the K lenses and sold them several years ago. So I couldn't test them in the recent resolution test. I actually tested K28/2. But after the test I found it need to be repaired, and deleted the K28/2 result. I will test it [again] . . .
The best among the lenses above, IMHO, is K28/3.5 in point of sharpness, contrast, resolution, and aberrations. The next will be FA28/2.8AL. This is just my opinion.