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07-31-2011, 10:20 PM   #16
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QuoteOriginally posted by civiletti Quote
I disagree to some extent with many of the comments in this thread. My take:

- The DA21 retest results on the k-5 are not stellar and not terrible. The DA18-55 has lower resolution at 18mm and higher resolution at 28mm, suggesting that it likely matches the DA21 at 21mm. The DA12-24 would likely test better than either.

- Sharpness [meaning resolution, not sharpness that can be altered in post-production] is not over-rated. It is one of the few optical parameters that cannot be enhanced much in PP. We can increase color saturation and tweak color balance. We can increase both overall and micro-contrast. We can correct linear distortion and remove chromatic aberration. In an image where maximum detail is desired, there is no substitute for a lens with high MTF50 results. If creamy bokeh is your nirvana, that's a different kind of image and only central MTF50 is critical, mostly at wide aperture.
Comparing DA21 to DA18-55 or DA12-24 is an apples to oranges comparison. Look at Voigtlander Color Skopar 20mm...less sharp in the corners (at least on FF). The challenge is to design a good compact wide angle lens.

07-31-2011, 11:14 PM   #17
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QuoteOriginally posted by civiletti Quote
I disagree to some extent with many of the comments in this thread. My take:

- The DA21 retest results on the k-5 are not stellar and not terrible. The DA18-55 has lower resolution at 18mm and higher resolution at 28mm, suggesting that it likely matches the DA21 at 21mm. The DA12-24 would likely test better than either.

- Sharpness [meaning resolution, not sharpness that can be altered in post-production] is not over-rated. It is one of the few optical parameters that cannot be enhanced much in PP. We can increase color saturation and tweak color balance. We can increase both overall and micro-contrast. We can correct linear distortion and remove chromatic aberration. In an image where maximum detail is desired, there is no substitute for a lens with high MTF50 results. If creamy bokeh is your nirvana, that's a different kind of image and only central MTF50 is critical, mostly at wide aperture.
There probably comes a point where, in most photographic endeavors, one reaches a sufficiency of sharpness (that is, resolved detail) that increasing "sharpness" simply has no bearing on the photo. I'll guess that when folks refer to sharpness as being "over-rated", they (at least I) mean that there is too much discussion about "sharpness" relative to other aspects of the lens in question.

As far as comparing the 18-55 & 21mm in terms of "sharpness", keep in mind that Photozone is testing one copy of each. The kit lens certainly has a reputation of having a large variation in sample quality, so of course take any singular test with an appropriate amount of sodium.
07-31-2011, 11:17 PM   #18
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what I find interesting is that distortion of 21/3,2 is a bit higher than that of 15/4
07-31-2011, 11:23 PM   #19
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QuoteOriginally posted by stanic Quote
what I find interesting is that distortion of 21/3,2 is a bit higher than that of 15/4
I'm not really surprised, as Photozone is only testing for barrel distortion and not keystoning. I am a tad disappointed at the 21mm's level of barrel distortion, though.

Nonetheless, I still want it.

07-31-2011, 11:24 PM   #20
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QuoteOriginally posted by luftfluss Quote
Nonetheless, I still want it.
second that
yeah the distortion is not really a problem with PP
08-01-2011, 02:47 AM   #21
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I just looked at the review of 21/3,2 on SLRgear, and what it says about sharpness is quite reassuring: "The 21mm ƒ/3.2 AL is a very sharp lens. When set to an aperture of less than ƒ/22, the lens didn't register much more than 1.5 blur units on our sharpness chart. I would put the optimal usage at ƒ/8, where image sharpness is tack-sharp across the whole frame. At ƒ/22, image softness ''degrades,'' probably due to diffraction limiting, to 2 blur units. All in all, excellent performance."
Pentax Lens: Primes - Pentax 21mm f/3.2 Limited SMC P-DA (Tested) - SLRgear.com!

do you think they are able to cope with the field curvature in their test or is this sample variation?

Last edited by stanic; 08-01-2011 at 04:54 AM.
08-01-2011, 04:30 AM   #22
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QuoteOriginally posted by philbaum Quote
I pick and choose lenses to take along based on what i will be doing, except the DA-21 always goes with me
Yep, me too. It's so small and reliable.

QuoteOriginally posted by philbaum Quote
i really don't care that the borders and extreme edges at f3.2 and f4 are not quite as good as the best of the primes. Life's about compromises and this is one lens that is an excellent compromise.
True again.

QuoteOriginally posted by fikkser Quote
18-55 might be worse in extremes at some f, but overall the 21 gets kicked on the nuts by a cheap kit lens in sharpness
I did that test, and I disagree. The center can be sharper with the kit (that's a compliment to the kit!) but across the whole frame, the 21 is much more even.

QuoteOriginally posted by luftfluss Quote
and I see some haloing around some of the 18-55's samples, which looks like some PP was done.
Nope, none was done.

Sharpness is the most overrated feature of a lens. You need a sharp lens, but arguing that this lens is sharper, that lens less sharp, when in the end both are more than sharp enough, means you are forgetting all that's making a picture great, and prefer to look at the capacity of a lens to resolve lines. Photography, once you have a reliable tool in your hands, is about light, not sharpness.
08-01-2011, 04:43 AM - 2 Likes   #23
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QuoteQuote:
- Sharpness [meaning resolution, not sharpness that can be altered in post-production] is not over-rated. It is one of the few optical parameters that cannot be enhanced much in PP.
Funny, I sold two prints this weekend taken with a point and shoot. One , printed as a 20x30 canvas.. was taken with my old 5 Mp Optio10... not one person complained about the lack of sharpness. Weird, those people need to read Pentax forum more.

08-01-2011, 04:46 AM   #24
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QuoteOriginally posted by asdf Quote
Comparing DA21 to DA18-55 or DA12-24 is an apples to oranges comparison. Look at Voigtlander Color Skopar 20mm...less sharp in the corners (at least on FF). The challenge is to design a good compact wide angle lens.
Again, it's a matter of priotiies. I come from the Pentax 6X7 system, so anything in the APS-C system is compact. If you are coming from a point and shoot, I imagine the DA12-24 can seem large.
08-01-2011, 04:53 AM   #25
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QuoteOriginally posted by luftfluss Quote
There probably comes a point where, in most photographic endeavors, one reaches a sufficiency of sharpness (that is, resolved detail) that increasing "sharpness" simply has no bearing on the photo. I'll guess that when folks refer to sharpness as being "over-rated", they (at least I) mean that there is too much discussion about "sharpness" relative to other aspects of the lens in question.

As far as comparing the 18-55 & 21mm in terms of "sharpness", keep in mind that Photozone is testing one copy of each. The kit lens certainly has a reputation of having a large variation in sample quality, so of course take any singular test with an appropriate amount of sodium.

As I wrote, most other optical imperfections can be overcome or at least ameliorated in post production. It's tough to add info that is not in the image. The higher the resolution of the sensor becomes, the more MTF50 of the lens matters. Your point about sample variation is valid. PZ's retest of the DA21 is consistent with results on the k-10, though. Did they use the same copy?
08-01-2011, 04:59 AM   #26
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QuoteOriginally posted by normhead Quote
Funny, I sold two prints this weekend taken with a point and shoot. One , printed as a 20x30 canvas.. was taken with my old 5 Mp Optio10... not one person complained about the lack of sharpness. Weird, those people need to read Pentax forum more.

Resolution is not everything in photography. If an Optio10 suffices, why spend more on equipment? I'd be using a D645 if I could afford one.
08-01-2011, 05:01 AM   #27
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QuoteOriginally posted by civiletti Quote
Did they use the same copy?
don`t think so
first copy provided by Patrick Pihl
second by Janosh Kalatech
08-01-2011, 05:09 AM   #28
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QuoteOriginally posted by bdery Quote
Photography, once you have a reliable tool in your hands, is about light, not sharpness.
And autos are about rolling, and loudspeakers about sound, and wine about alcohol, but folks pay a lot of attention to small variations in their performance, not without good reason I think.
08-01-2011, 05:17 AM   #29
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QuoteOriginally posted by normhead Quote
Funny, I sold two prints this weekend taken with a point and shoot. One , printed as a 20x30 canvas.. was taken with my old 5 Mp Optio10... not one person complained about the lack of sharpness. Weird, those people need to read Pentax forum more.
Heheh... I take pictures of parents and children at the children's centre I work at and some are displayed for people to see. Far and away the best shot is of a kid throwing some water at me. I took this shot with a 4-5 year old P&S, so crap I don't even know the brand, maybe a Kodak or something. The rest with my K10D and fast primes. They are all poster size. No way would I have got that shot with the K10D. OK, there are other nice shots I wouldn't have got with the P&S, but still. The resolution and sharpness looks no different, even tho the prints are big.
08-01-2011, 08:33 AM   #30
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QuoteOriginally posted by bdery Quote
Sharpness is the most overrated feature of a lens. You need a sharp lens, but arguing that this lens is sharper, that lens less sharp, when in the end both are more than sharp enough, means you are forgetting all that's making a picture great, and prefer to look at the capacity of a lens to resolve lines. Photography, once you have a reliable tool in your hands, is about light, not sharpness.
+1 on that!
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