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12-31-2008, 09:12 AM   #1
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DA21: Why such a big difference between these two tests ?

Well, I just got my DA21 and don't have much time with it to make any conclusions. I know some love this lens and some don't. I saw these tests deal with the sharpness of this lens. They show markedly different results. One shows the edges soft throughout the aperture, the others shows the edges sharper. At f3.2 the center vs edge sharpness is astronomically different. This i a 'limited' series lens, which shouldn't have much market variability.

Pentax SMC-DA 21mm f/3.2 AL Limited Review / Test Report

Pentax SMC-DA 21mm f/3.2 AL Limited Interchangeable Lens Review

Thank you.

12-31-2008, 09:18 AM   #2
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Consider that the testing procedures themselves are introducing the variables. Very few people actually know how to set up a lens test, and the internet just seems to propogate them.
I have found the 21 to be an excellent performer indeed.
12-31-2008, 09:29 AM   #3
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I would say, now that you are fortunate to have one in your hands, shoot with it and see if it pleases you.
I only had a brief experience with the DA21. I had to send it back because it had focusing problems.
12-31-2008, 09:42 AM   #4
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the ephotozine review shows the edges to be sharper than the center? maybe there's a bug in how they tested it? personally, my experience was more like Photozone's, there is improvement in stopping down

to me the lens was pretty good, but not OMG fantastic. you pay a premium for the build quality and the small size as expected.

12-31-2008, 10:25 AM   #5
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So, one plausible reasoning is methodology. I would have assumed that both methods are close enough to not give this much of a difference, it is like testing two different lenses ?, but I could be wrong.

I was also wondering whether the different bodies (K100D vs K10D) used for the testing, would show this much difference as well.


I am not trying to figure out whether this lens is good or not, or which of the tests is correct. Ignore the lens and even ignore the absolute results. I am just wondering what are plausible reasons for such a difference of the same lens between two tests, that's all.

-Methodology
-Camera body
-sample variations

etc.

Thanks.
12-31-2008, 11:02 AM   #6
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That's an interesting question!

Both sites use similar methodology (take pictures of a nearby target and use imatest to calculate MTF values). However, photozone uses identical targets (quadrants) at the center, corners, and extreme corners:

Photozone Lens Test FAQ

while ephotozine appears to use different targets for the corners (quadrants) and the center (test chart)

How ePHOTOzine does lens tests

also, distance-to-target may be different between the two tests (I could not determine this from the data provided), and ephotozine doesn't describe the focusing procedure used.

It seems likely that differences in testing methodology alone explain the different results.

BTW, my experience with the DA21 is consistent with the photozone results.
12-31-2008, 11:37 AM   #7
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QuoteOriginally posted by troyz Quote
BTW, my experience with the DA21 is consistent with the photozone results.
Me too. I love the DA21, but regardless of the field of view on APS-C, it's still an ultra-wide prime - and like almost all ultra-wide primes, it is much sharper in the center than the edges. It's just a limitation of optical design. I stop down to f8 or more to get decent edges, and I notice that at closer focus distances the edges tend to get a bit worse. At infinity distance the edges are pretty good, which makes it a good landscape lens when stopped down a bit. The center performance is extremely sharp at all apertures, and like all the DA Limiteds it has very good contrast and color rendering.
12-31-2008, 11:37 AM   #8
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I just did some product shots of my copy of DA 21mm f/3.2. I love doing product shots of this lens. It is a beautiful lens. I like it for landscape shot and in traveling. I find it not ideal in indoor shot for me when I tried it on K10D. I will try it again with K20D and perhaps add in a bounced flash for help when needed. If it has f/2.8, it will be ideal for me.


Pentax DA 21mm f/3.2 limited


It is a beautiful lens, enjoy it


shot with inexpensive Sunpak 422D bounced flash



Ever since I bought the Tamron 17-50mm f/2.8 and later exchanged it for Sigma 17-70mm f/2.8, I find myself going for the zoom rather than the fixed prime due to less lens change especially in traveling.

And I have satisfactory wide end results wide open in f/2.8 with both zoom lens. Have anyone done some comparison between the 21mm limited to popular zooms such as the DA* 16-50 and Tamron 17-50mm f/2.8 in the 21mm focal length? I think I remember seeing a comparison in PF recently between 21mm and Tamron 17-50 f/2.8 and I recall results quite close in a brick wall comparison.


Last edited by hinman; 12-31-2008 at 12:32 PM.
12-31-2008, 11:48 AM   #9
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blende8 did this test here
Resolution/Contrast of the DA* lenses - a comparison: Pentax SLR Talk Forum: Digital Photography Review

and then Sinan (sft here) did this test here
Extensive DA*16-50 vs. DA21, FA31, FA50 and DA70 Test: Pentax SLR Talk Forum: Digital Photography Review
with revised results on the DA21 here
Conclusive DA*16-50 & DA21, FA31 & FA50 Lens Test: Pentax SLR Talk Forum: Digital Photography Review

note i think Sinan has since sold his DA* for a Tammy
12-31-2008, 05:01 PM   #10
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It is a known issue that the DA21 doesn't focus well with the K10D.
When used on the K20D, all the focusing gremlins are gone everything is perfect.
Bottomline I wouldn't read too much into tests that still use the K10D as the benchmark.

Personally, I think the DA21 is the most versatile of the DA Limiteds and the only one I would consider keeping.

Last edited by creampuff; 12-31-2008 at 05:07 PM.
12-31-2008, 06:42 PM   #11
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QuoteOriginally posted by hinman Quote
And I have satisfactory wide end results wide open in f/2.8 with both zoom lens. Have anyone done some comparison between the 21mm limited to popular zooms such as the DA* 16-50 and Tamron 17-50mm f/2.8 in the 21mm focal length? I think I remember seeing a comparison in PF recently between 21mm and Tamron 17-50 f/2.8 and I recall results quite close in a brick wall comparison.

Recently I purchased another used copy of DA 21 to complete my DA series. I also have the Tammron 17-50. As I was testing the KatzEye I happend to take similar shots between DA 21 and the Tamron 17-50. Nothing scientific but in this test the DA wins. However, I think the results of the Tamron could be improved by manual focusing. These shots were taken with AF.

The first one is with DA 21mm:





The second one is with Tamron 17-50mm:




DA 21mm Crop below:



Tamron 17-50mm crop below:


Last edited by Stratario; 12-31-2008 at 06:48 PM.
12-31-2008, 07:16 PM   #12
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K2000/K-m

QuoteOriginally posted by creampuff Quote
It is a known issue that the DA21 doesn't focus well with the K10D.
When used on the K20D, all the focusing gremlins are gone everything is perfect.
I'm seriously considering this lens to give me a 21/35/70 kit for my K-m. I wonder if anyone has experience to confirm that focus issues are better with 21/K-m than K10D.

Todd
12-31-2008, 08:07 PM   #13
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QuoteOriginally posted by gnaztee Quote
I'm seriously considering this lens to give me a 21/35/70 kit for my K-m. I wonder if anyone has experience to confirm that focus issues are better with 21/K-m than K10D.

Todd
FWIW, I use that same trio with the K200D, and have no focusing problems. The Km/K2000 should be at least as good.
12-31-2008, 08:32 PM   #14
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I found it a bit strange that ephotozine listed one of the 3 main negatives to be Price. Would they say that about an L lens?

QuoteQuote:
In summary, the positive points of the SMC Pentax DA 21mm f/3.2 AL Limited are:
Compact in the extreme
Good resolution across the frame
Good build quality gives confidence in longevity

The negative points are:
Some barrel distortion
Some CA when stopped well down.
Price
12-31-2008, 10:25 PM   #15
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Da 21mm ltd has been misquoted to have severe fringeing issue. I found the opposite result. I am not a fan boy and very critical of gear. Da 21mm ltd does not have the severe purple fringe under the typical harsh Australian sunlight comparing to other lenses of its league.

Absolutely no concern about sharpness (well it is f3.5; it better performs). Just the background bokeh can be chalky even with the most forgiving background elements like green lawn.

When this lens is used for night photography, the images tend to be quite clear with a little popping colour.

This is my personal field experience. Some of my photog friends ignored these lab testings altogether. It is really about how the gear applies to a photographer's needs rather than just about sharpness. My friends would prefer to hear from other friends' personal experience with different applications to the particular lens instead of some reviews with testing sample photos rather mediocre.
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