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12-16-2009, 10:01 PM   #16
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if the OP doesn't mind, maybe he could try out the manual focus 28s' ? and see if there is any difference.

12-17-2009, 02:04 AM   #17
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Here is my test of the contrast of the F28 versus the FA28:

Contrast F28 / FA28
I have found the reduced contrast at f2.8 to be the only significant difference between the two lenses.

Else I have noticed that the focal length of the F is slightly shorter than that of the FA, about 3-4% (= ca. 1mm focal length), but I don't know which one is closer to 28mm.

Btw. the best 28mm from Pentax is in my view the M28/2.0.
It is optically and mechanically as excellent as the K28/2, but much smaller.

Last edited by blende8; 12-17-2009 at 03:23 AM.
12-17-2009, 04:01 AM   #18
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Wieland, that is quite a bit of difference there. I remember this test of yours from before, and I've heard from owners who had both preferring the F version. That wash the reason for me to hunt down the F28/2.8. It is a useful fl, and a very nice lens.
12-17-2009, 06:22 AM   #19
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Thanks to all who replied

Thanks guys, my buyer's remorse has totally dissipated. I really enjoyed the photos, but especially your assurances and blende8's test showing performance wide open. This lens will be used primarily at f2.8, and IME good contrast is a more desirable attribute than pure MTF sharpness.

Pentaxor, I will definitely post a comparison of F 28mm vs Image A 28mm vs FA 35mm.

12-17-2009, 07:29 AM   #20
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QuoteOriginally posted by blende8 Quote
Here is my test of the contrast of the F28 versus the FA28:

Contrast F28 / FA28
I have found the reduced contrast at f2.8 to be the only significant difference between the two lenses.

Else I have noticed that the focal length of the F is slightly shorter than that of the FA, about 3-4% (= ca. 1mm focal length), but I don't know which one is closer to 28mm.

Btw. the best 28mm from Pentax is in my view the M28/2.0.
It is optically and mechanically as excellent as the K28/2, but much smaller.
Those results from the F28/FA28 comparison remind me exactly of what I encountered when testing the two lenses. The FA28 appeared to bleed light into darker areas and mush colors together when wide open. Wonder what good the AL optics did for IQ? Maybe slightly reduced CA or something? I don't know.

As for the best 28mm, I've read a lot of good things about the old K28/2, and have always kept an eye out for one. I missed a chance to buy a nice looking one for $200, but I was too slow to pull the trigger. sigh. next time.
12-17-2009, 01:21 PM   #21
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Talk about slow to pull the trigger. I shouldn't have read this thread! I missed out on an F28 by minutes in the marketplace a few weeks ago, and the price was really good. I knew I didn't really need it, so maybe my hesitation was part of my LBA recovery?

The K28/2 is based on the same formula as the Zeiss Distagon 28/2 (or vice versa), and it's pretty large. From what I've seen, the contrast on the Zeiss is a little better, but the Zeiss is a $1000+ lens!
12-30-2009, 11:29 PM   #22
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I returned the F 28mm to KEH. It was backfocussing pretty badly. I don't think I can conclude anything from its brief stay, since it was clearly defective.

I replaced my K100DS with a K-x. Both the K-x and K20D meter my Image A 28mm 2.8 properly, so I guess I'll just stick with that.
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