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08-25-2009, 01:14 PM   #1
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"Best" AF sharpness for K20?

I want to get a good walk-around prime for my new K20. I have a good (but heavy) Tamron 28-75 for general use, and just acquired an A50 f/1.7 through a Forum trade that is brilliant, but I'd like to add a Pentax AF prime "normal" lens for my mainstay.

All the various ratings and test sites generally put the FA 31, FA 35 f/2, and the FA 43 at the top of the list for resolution, but I also read "sharpness" is resolution + (micro)contrast and contrast is subjective and can't really be measured.

I like natural outdoor light, and convert most images to B&W. And I like what I perceive as the sharpness of the A50 (100 % crop below), so would like some input on selecting that one-stop-sharpness AF lens that can deliver comparable IS.
Brian


08-25-2009, 01:38 PM   #2
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i consider myself pretty new and casual to lens rendering, but I have / owned all three of the lenses you mention and in my opinion the FA43 is probably the most contrasty stopped down
08-25-2009, 01:45 PM   #3
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I don't know the other lenses, but I use the 43 extensively just as you intend to - and find it very alive indeed, resolution and contrast wise.
08-25-2009, 01:53 PM   #4
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Don't forget the DA 40mm; sharp, colorful, and contrasty.

08-25-2009, 01:59 PM   #5
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Lots of primes in this range are very good for IQ.
Can even include the DA 35 macro in there too.
08-25-2009, 03:34 PM   #6
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QuoteOriginally posted by FHPhotographer Quote
All the various ratings and test sites generally put the FA 31, FA 35 f/2, and the FA 43 at the top of the list for resolution, but I also read "sharpness" is resolution + (micro)contrast and contrast is subjective and can't really be measured.
That's not *entirely* true - MTF is a method for measuring the sharpness as defined by resolution+contrast. How well it does at capturing this is something for people with more expertise than I to argue about, but there no doubt it does measure more than just resolution.

All of the aforementioned lenses - as well as the DA35 and DA40 - do very well in MTF scores. Well enough that it's almost pointless to worry about the tiny differences between them. According to the numbers at photozone, the 43 is weakest of the bunch at apertures larger than f/2.8, but the strongest from f/2.8 to f/4. As the review of the DA40 notes, though, the differences are probably detectable only by their MTF testing equipment and wouldn't be visible to the naked eye. And even so, there are tradeoffs, as some of the lenses that test sharpest at the center don't do so well in the corners. Still, we're talking about hair-splitting differences. These are all very sharp lenses.

Which is to say, choose between these based on focal length, based on maximum aperture, based on size, based on price, based on focus speed, based on close focus ability, or even based on the "pixie dust" some lenses are alleged to contain, but there's no difference between them in sharpness worth giving much weight to.
08-25-2009, 04:19 PM   #7
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QuoteOriginally posted by FHPhotographer Quote
I want to get a good walk-around prime for my new K20. I have a good (but heavy) Tamron 28-75 for general use, and just acquired an A50 f/1.7 through a Forum trade that is brilliant, but I'd like to add a Pentax AF prime "normal" lens for my mainstay.

All the various ratings and test sites generally put the FA 31, FA 35 f/2, and the FA 43 at the top of the list for resolution, but I also read "sharpness" is resolution + (micro)contrast and contrast is subjective and can't really be measured.

I like natural outdoor light, and convert most images to B&W. And I like what I perceive as the sharpness of the A50 (100 % crop below), so would like some input on selecting that one-stop-sharpness AF lens that can deliver comparable IS.
Brian
The image you posted looks a little oversharpened to me.
08-26-2009, 05:21 AM   #8
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The sharpest lens Pentax made is the FA 50 macro, according to many. It's the sharpest I've used, for sure, but at this level differences in sharpness between the 50 macro and any other lens is marginal at best. You would be hard-pressed to find a difference between pictures taken with it or a limited, for instance, or a FA 35 f2... I believe the skills of the photographer and the post-processing will have much more of an impact than any basic lens capabilities.

Shopping for a lens based exclusively on sharpness doesn't make much sense to me. My only PPG entry was shot with the Sigma 17-70 zoom, a great lens but not my sharpest by far.

08-26-2009, 05:04 PM   #9
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QuoteOriginally posted by Nesster Quote
I don't know the other lenses, but I use the 43 extensively just as you intend to - and find it very alive indeed, resolution and contrast wise.
Nesster, this is a great shot in the terms and use I am looking for... the tonal range, sharpness, etc. is first rate and what I want to work towards (within the limitations of my ability, of course). This is a K100 with the FA 43? Did you shoot RAW? What B&W conversion did you use? Thanks,
Brian
08-26-2009, 05:38 PM   #10
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QuoteOriginally posted by Wheatfield Quote
The image you posted looks a little oversharpened to me.
Having used an A50/1.7 myself, that kind of sharpness seems typical for this lens. Just IMHO of course

I have the FA 35 and while it renders very well, I can't help but just go back to the Tamron 28-75 time and time again... I wonder why though I'm guessing it's because they're equal in sharpness and I'm just too used to the Tammy rendering. I probably just haven't spend enough time with the lens. So take it with a grain of salt

I have a hard time justifying the DA 40 since it's the same speed as the Tammy, and FA35 is faster and relatively small. But M40+ZX-7 is such a nice, compact combi that I'll probably get the DA 40 too someday.
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