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04-19-2009, 07:13 PM   #1
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Bad DA 21 or expectations too high?

Hello all. I just bought a K20D, DA70 and DA21 to have a small, lightweight travel system. The first images from my DA21 seemed to be unacceptably blurry so I started a long process of testing for front/back-focus. This turned out to be really difficult with the wide-angle and smallish maximum aperture. To complicate matters, nothing ever really looks clear, just some things are more blurred than others. With a lot of effort and frustration, I've settled on an adjustment of +10 for the best center focus. Trouble is, even with this adjustment, the focussing is inconsistent--I can see on the focussing scale that it doesn't consistently focus to the same distance every time.

When I do get the center as sharp as it can be, I'm surprised at how out of focus the corners are. If all the corners were equal, I'd suspect that that's as good as the lens gets, but the bottom right quadrant is far blurrier than the other 3 corners. This got me wondering, maybe my camera was not aligned perfectly with the test chart. Furthermore, how does this compare to my nearest Canon lenses? Without moving the tripod, I mounted my Canon 40D with 28/1.8 and shot wide open. Much better results and all four corners were equal confirming that my alignment was good. Of course the the field of view was smaller (45mm equivalent vs. 32mm) so I slipped on my 17-55/2.8IS and compared the two lenses with the same field of view and even at f/2.8 the 17-55 showed much better resolution and sharpness than the DA21 all over the frame.

Now I realize the DA21 is not considered to be the best of the DA Ltd lenses, but I had much higher expectations. Is it possible I got a bum lens? In 25 years I've never done lens tests, but the initial images were just too soft and required further investigation. Shots I took today with the focus adjustment are much improved, but after the results of my testing, I'm just not sure whether I should accept the lens. I have until Friday to return/exchange the lens. Unfortunately the store is 90 minutes drive away.

Out of curiosity I decided to compare the DA70 to my EF70-200/4 IS lens. Central sharpness is pretty similar, slight edge to the Canon, edge sharpness is definitely better on the Canon, but I'm still pleased with the DA70. The DA70 is much better than the DA21. To be honest, I definitely had higher expectations for this system. I'll live with the performance of them for the compact size and I've just made arrangements to sell off my EF28/1.8 and EF85/1.8 since they're so much larger.

Oh, and for those who are about to ask, the camera was mounted on a tripod, mirror lockup and timer was used, images taken in RAW and processed in Lightroom with equivalent settings used, and many images were taken with me using only the best images for comparison purposes. I tried many methods of determining front/back focus (books on a shelf, test charts printed and shot at 45 degrees and finally a pattern on a computer screen to create moire which seemed to the most reproducible and precise method).

So how about it--do you think I have a bum lens or am I just expecting too much?

04-20-2009, 12:21 AM   #2
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Regarding your problem, it seems that there could have been some decentering issue with the lens.

Aperture f3.2 is a pretty dim for a prime. This maximum aperture would have adequate depth of field covered within the frame. A gross out of focus blurr is really unlikely unless a close focus approach is attempted.

I suggest to send this limited to pentax for an evaluation instead.

Getting back to this particular limited, it has strengths and weaknesses just like any other lens. However, Some weaknesses could work as advantages for certain photographers.

The lens is known for its unsharp corners with vignetting at f3.2 but it does not matter matter if aperture f8 is used for landscape. For night scenery, f4 is far more than sufficient to get the depth of field. The rest could use a little USM sharpening via Benjikan technique. This is relatively simple.

What makes pentax da limited special is the strong colour and excellent contrast. This type of characteristic is hard to produce from photo editing. A signature look for pentax users. Da limited does cast that rich glow to certain colour embedded with strong gradient to the image. The micro contrast from da limited also pop the images interestingly.

Da 21mm ltd in particular does not seem to have that strong micro contrast like any other da limited. Hence appear a little soft everywhere. I have found a way to get around to it by isolating the edges out with selection placing the dodgeing along these selected edges. It seems to bring back a bit more micro contrast instead.

This thin pancake prime is a great lens just for being so small. Consider a 25 km hike in the mountains. A light wide prime like this is very valuable. There is a lot a lot of envy from canikon users who hike along with me feel extremely jealous. After all, a canon EF 20mm f2.8 is quite an extremely dodgy lens. Canon EF 24mm f1.4 is 550 g or so and Nikon 12-24mm f2.8 is 1 kg. By comparison, this type of heavy lens does add a lot of stress to a long trip. Considering the tough nature of the hike, heavy lenses are nuisances.

Speaking to a casual street shoot, a light small prime is so insignificant to pedestrians or museum shooting. No one really cares about the photographer who can feel free to get the "moments" when they want to.

I have used sigma 24mm f1.8 in the street. Besides all the bravo about the fast autofocusing of this prime as well as its incredible resolution in its images, the colour and contrast are seriously inferior to Da 21mm ltd. What is more is the bulky nature of the prime that can frighten a lot of people.

I would not quickly dismiss this lens as I have previously done so. A great lens to use in deed and I had been using this for daily walk around so far. Not much touch up is needed. However, I would not say that this is the best landscape prime I have ever owned.

Some images from Da 21mm ltd








Pentax Da 21mm ltd gallery

Keep us updated.
04-20-2009, 03:04 AM   #3
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I had a similar problem with the 40mm LTD, ie I had never done a focus test ever until i got this lens. I looked at the images wide open and then trashed them all. This happened with pretty much all the wide open shots. I adjusted the AF on the k100d and there was still a backfocus issue. So i borrowed another 2 K100d bodies. It did it on all of them. I got the lens replaced. The new one is great. It's definitely my favorite lens. I also got the 70 LTD and it is also very very nice and i had no quality problems with it.

Anyway, I wanted to chime in on what Roentarre is saying about the colors and contrast. The two limited i own are fantastic in color and contrast. I'll hit the + button on the contrast in PP and then turn it back down again. It just does not need it. The colors also don't need any tweaking. These two LTDs i have reduce the work needed in PP to get lovely images.

Go and have a look at roentarres gallery and have a look at the colors and contrast... That is whati love most about the limited. But I will watch this thread closely as I considering buying the 21 BUT..... i may look for alternatives as it is the most expensive and seems to have the worst reputation. Why?

cheers
mike
04-20-2009, 04:07 AM   #4
RaduA
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QuoteOriginally posted by bpjod Quote
Out of curiosity I decided to compare the DA70 to my EF70-200/4 IS lens. Central sharpness is pretty similar, slight edge to the Canon, edge sharpness is definitely better on the Canon, but I'm still pleased with the DA70. The DA70 is much better than the DA21. To be honest, I definitely had higher expectations for this system. I'll live with the performance of them for the compact size and I've just made arrangements to sell off my EF28/1.8 and EF85/1.8 since they're so much larger.
Hello,

The way I see it a DA70 mounted on a 14,6Mp K20D cannot be *definitely* less sharp (especially if you meant similar aperture of f4 and above) than even one of the best zooms available mounted on a 10Mp camera. The DA70 is razor sharp at f4 and with a very even resolution across the frame and my suggestion is to verify if you didn't applied a global amount of AF adjustment to all lenses in K20D thus messing with the DA70.

Regards,
Radu

04-20-2009, 05:01 AM   #5
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It's probably not the sharpest tool in the shed, but it has always been enough for me.

When I first got mine, I had some focus issues and I was a bit concerned. After fixing that up it was fine. I'm not really a corner sharpness guy though, most of the time my corners are out of focus anyway.

My K10D is pretty jacked up to start with. I bought it used, the matte focus screen was never properly shimmed and there was a bit of backfocus going on in the AF system. Now I'm running it with a china focus screen, cut up post-it notes as shims, and +100 in debug mode adjust.. but my photos seem mostly in focus!

I sold my 16-45 to get the da21 and don't regret it. 16-45 just couldn't go places. Photo is better than no photo.



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04-20-2009, 07:05 AM   #6
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If you can't get anything sharp, then return the lens for replacement. The DA21 is a very good little lens, decently sharp wide open and very sharp as it is stopped down.
04-20-2009, 08:38 AM   #7
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Original Poster
Thanks for the replies so far. As the image is so badly out of focus in the bottom right quadrant compared to the other three quadrants I'm suspecting a misalignment of the optical elements. I think tomorrow I'll try to swap it out for another copy. I really want to like this lens; Roentarre, you listed exactly why I picked up the Pentax system as my travel system. I'm happy with my Canon kit when I'm shooting from a car, but the lenses are too bulky for a nice, light travel/backpacking/bicycle touring kit.

Mike, it's reassuring to hear your experience. I'm hoping I have a similar happy outcome.

Radu, no I didn't apply the focus adjustment globally. The DA21 is at +10, the DA70 at +3 (since I was adjusting the DA21, I thought I'd try the DA70, not that I was unhappy with it's performance). At 100% on screen, the EF70-200/4 IS does appear "sharper" than the DA70. I did forget to take into account the higher resolution of the sensor. Perhaps if I resize both to the same size I'll see that their performance is equal. Not that there's much in it, they're both great lenses. It does make me wonder about the wisdom of adding more megapixels though.
04-20-2009, 09:34 AM   #8
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QuoteOriginally posted by bpjod Quote
Trouble is, even with this adjustment, the focussing is inconsistent--I can see on the focussing scale that it doesn't consistently focus to the same distance every time.
I've ever encountered the same problem in my Sigma 30/1.4. Then I realized it has centering defect issue. It has been in Japan for 1 month, still no news.

04-20-2009, 01:06 PM   #9
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I'd send it back if I were you. I've never had any problems like this with mine.
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