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Old Apr 24, 2007, 12:45 AM   #1
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Sunday I was out taking pictures of a pretty sunset with the K10 and the DA 50-200. Once again I noticed the right side of some of the pictures seemed to be blurred where the rest of the picture was sharp - and the object that was blurred was a mountain ridge around a mile away, so there shouldn't have been any DOF or focus issues, if the rest of the ridge was sharp.

So today I took a series of pictures with both the K10 and the K100 and the DA 50-200, both in raw and P mode (I'm standing directly across from this building, standing square almost in the center of it, on some steps that are the same height as the steps in the picture, far enough away so that the lens is focusing at infinity). I opened them in Lightroom,without any processing of any type,and used the "compare" feature to look at the pictures from both cameras, taken at the same focal length (used the marked focal lengths, so they would be the same). One of the neat things with Lightroom is that you can zoom in 100% at the exact same point in the frame (not necessarily the same spotin the picture, if you didn't frame them exactly the same). Then I did a "print screen," pasted that in a new photoshop file, cropped out the extra menu/bars top and bottom and saved without resizing.

I've uploaded them to flickr - since they are my screen size (a little less than 1280x1024), they are too big to post here. Can several of you please take a look at them and let me know what you think. Is this normal for the DA 50-200, or is mine a problem? Or is it the camera? I'm confused. What do you think? And I recently cleaned the glass, making sure there were no smudge marks on it (always a possibility).

The album is at: http://www.flickr.com/photos/5744707...459366/detail/- let me know if the link doesn't work right.

P.S. It's easier if you look at the large size files of the 100% versions, rather than the thumbnails - maybe I'm making a mountain out of a molehill. The full frame versions are more for orientation for the two pictures, rather than useful for comparisons.

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Old Apr 24, 2007, 4:59 AM   #2
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The test images are not the best subject for comparison - tiled roofs produce strange effects when reduced in size.

Perhaps you could post the sunset you refer to.

INHO, the subject should be in focus from side to side - unless there's something in the foreground that wasn't too obvious that obscured the focus at infinity.

I have a *istDS with DA 50-200mm lens & haven't noticed any problems at all.
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Old Apr 24, 2007, 9:04 AM   #3
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Will brick do the same thing as tile roofs? That's actually what I was looking at - the right hand side middle to lower corner seems to me to be more blurred than the same area on the left (brick stairs, brick building and the bicycles/people). I don't have a comparison shot to go with the K10 sunset picture, but will try to find something else today, also will try to shoot something with another lens.

I've tried to cleanthe glasswith a lens cleaning kit and don't see any obvioussmudges - is thereanything special I might try?
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Old Apr 24, 2007, 10:14 AM   #4
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Do have a UV filter installed on this lens? I once had a UV filter that was defective and produced somewhat similar results. Exchanged the filter and everything was good after that.
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Old Apr 24, 2007, 10:38 PM   #5
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I had some trouble with a cheap UV filter not long after I bought the DS, and I've just never gotten around to buying good ones for my lenses, so not the problem. Sure wish it were - that's a quick fix.

Oh well, if no one has any suggestions about cleaning the lens (do I use the lens cleaning solution that came with the kit or not?), I may just junk the lens (hate to do that, but it's driving me nuts the way it is). I thought it was interesting that the blurriness wasn't consistent, being more obvious at 80 and 135 - didn't reallynotice it at 50 or 200, why I thought it might not be some unseen smudge. I really hate this because I use this range all the time and I won't have anything to replace it. :sad:
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Old Apr 25, 2007, 1:50 AM   #6
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Why don't you ask Pentax to fix it? Is it out of warranty?
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Old Apr 25, 2007, 1:59 AM   #7
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How does it do with the kit lens or is the 50-200m your only lens?

Sounds more like a lens than camera flaw. And if no filter, TC or anything involved, I'd say you got a bad 50-200mm.
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Old Apr 25, 2007, 9:05 AM   #8
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Unfortunately, just out of warranty. Not sure that they would have covered it anyway, since the lens has a ding or two on it - if it's something that's been knocked out of alignment they could say it's my fault. I'm careful withmy equipment, but I do cartit around all the time and use it all the time.

I think I see the problem with both cameras (was hoping someone would confirm that for me, but perhaps the pictures posted aren't clear enough), though it looks worse with the K10 (do the larger number of pixels cause images to look softer on computer monitors? Or is it that the camera can now resolve better than the lens is capable of?). Or perhaps I'm just dreaming the whole thing.

Does anyone have suggestions about lens cleaning?
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Old Apr 25, 2007, 2:50 PM   #9
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Hi Harriet - I'm not sure if I can help on this, but I saved a link I saw on Dpreview a while back. It has a link to a test chart on checking focus problems. The chart info is for the D70 Nikon, but it will work on any camera. Here's the link to a fellow that played with this and it has the link to the test chart.

http://forums.dpreview.com/forums/re...398&page=1

I'm not sure what you do if your focus problems are only on one lens, but I thought it would be interesting to test your most common lenses just to know they are in sharp focus. The test chart looks very interesting. I have noticed a problem when I focus at infinity on my Macro lens and I am going to do this test to see if I have focus problems on it, but haven't had time yet. Anyway, hope this helps you - Bruce
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Old Apr 25, 2007, 10:22 PM   #10
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That link is a good one - I've actually tested several of my lenses and the focus point with manual focusing. My K10 tested within specifications for all my lenses, and the focus light was very close (didn't test the A300 - did it indoors and couldn't get far enough away to focus). There is more behind the focus line in focus than in front of it (slight backfocusing) but the line itself was sharp, so it meets specs. Knowing this, I always try to focus on the closest thing I want in focus.

My problem with the DA 50-200 isn't with the focus overall - it's that one side of the lens is blurry compared to the other side and the center. It's more noticeable with certain focal lengths - I don't see it muchat the extreme ranges (50 and 200). If it were a smudge I would have thought it would be consistent no matter what focal length it was at, perhaps being lessened with a change in aperture, but that was my first thought (I did clean the lens, and don't see any smudge or scratch on the glass).

To give you an example (sorry to post as big of a file as this, its easier to see what I'm talking about withwhat is almostthe size of my monitor)- here's a screen shot of a 100% crop, center section of a picture taken at 95mm. The K10 is on theleft (obviously) and the K100 on the right. Lightroom shows the same spot on your pictures in comparison mode, you can't scroll the pictures separately so they don't line up exactly (I was handholding the pictures and didn't quite get them exactly the same). I thought the center is quite sharp with both cameras at this spot:



Now here is the left side of the same photo - still looks pretty sharp to me, not that much softer than the center, certainly about what I would expect, I think (remember these are 100% views).



Finally, here is the right side. To me it looks significantly blurrier than the left side.



Just to give you an idea of the full frame picture, here's what they look like (this is flickr's smaller size, so is reduced from the monitor size of the ones above, you can't tell much from it other than to see what points I used in the crops above):



So is there some type of blurriness on the lens that I can't see? Is there something that is wrong with the lens internally that would cause this? If the former, does anyone have a suggestion on cleaning the glass? I really hate to write-off this lens.
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