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09-05-2007, 10:27 AM   #1
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Vexing lens problem

Purchased a K100D and 18-55 plus 50-200 mm Pentax lenses (kit). At first the pics looked good when using the 18-55. When trying to use the 50-200 Pentax lens I started noticing that images were focused but lacked any real detail. To be more specific. I can take a picture from the 18-55 and zoom in and actually see incredible image detail, well for 6 mp anyway. With the 50-200 the image detail goes all to heck. It is not so bad with close ups, but is bad when taking a picture of something far away (camera seems to be setting the focus properly). It just lacks resolution and detail. Am presuming it is the lens, but guess it could be something in the body.

Have tried manual and auto focus and results seem the same. Should I just take it to a service center, and what would I tell them?

Ed

09-05-2007, 11:35 AM   #2
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Can you post some examples (with EXIF data)?
09-05-2007, 01:52 PM   #3
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this sounds like you might be front/rear focusing with the 50-200. try shooting a few shots in MF and forget the focus confirmation light and beep. see if there's a difference .. try different APs also.
09-05-2007, 05:06 PM   #4
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Ah, just like above.. If you close the lens down, the images will sharpen up some. However, you may have just gotten a bad copy, it may have gotten jarred in transit, ect. If it really gets bad, why not go to a camera store, and try a few frames with a second copy. If it is much better, why not send yours back and get a new copy?

However, if you really want good images, why not sell it, and get a zeiss 180 F/2.8 for m42 mount??

09-06-2007, 06:51 AM   #5
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I am new to this forum...if I upload a jpeg will it contain all the data?
09-06-2007, 06:53 AM   #6
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Have pretty much tried that. The weird thing is that it does OK when the subject is to near infinity...say 20 or 30 feet away, or closer.

Ed
09-06-2007, 06:54 AM   #7
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Am stopping down to f8 f11 and can not afford the suggested lens...unless you are willing to take low monthly payments :-)
09-06-2007, 07:32 AM   #8
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QuoteOriginally posted by mattdm Quote
Can you post some examples (with EXIF data)?
Uploaded two pictures to the User Picture Forum, Nature category. The Magpie looks pretty good and is at medium distance to lens (20-30 feet). The second shot is more than a hundred and fifty feet away and shows how pictures focused near infinity lose clarity and detail. There is no part of that image that looks in focus and detailed, have many like it

09-06-2007, 07:50 AM   #9
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QuoteOriginally posted by Justed Quote
Uploaded two pictures to the User Picture Forum, Nature category. The Magpie looks pretty good and is at medium distance to lens (20-30 feet). The second shot is more than a hundred and fifty feet away and shows how pictures focused near infinity lose clarity and detail. There is no part of that image that looks in focus and detailed, have many like it
Justed, to make you feel better, as in "misery loves company". I have the exact same problem with the 50-200. Anything further away than about 100'/30M is sadly lacking in detail. I solved the problem (sorta) by getting a second hand Pentax K 300mm F4. They are quite reasonable, if you hunt around and they have much better resolution, not to mention being a bit faster.

NaCl(I like the 18-55 a lot and dislike the 50-200 a lot)H2O
09-06-2007, 08:38 AM   #10
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Way too much pixel-peeping!
Badly warped sense of reality-little or no notion, much less understanding of resolution.
Example images of absolutely no value in either illustrating the alleged problem or working toward a solution.

You might be able to post-process for a slightly better presentation, but your equipment is performing nominally.

QuoteOriginally posted by Justed Quote
Uploaded two pictures to the User Picture Forum, Nature category. The Magpie looks pretty good and is at medium distance to lens (20-30 feet). The second shot is more than a hundred and fifty feet away and shows how pictures focused near infinity lose clarity and detail. There is no part of that image that looks in focus and detailed, have many like it
09-06-2007, 09:22 AM   #11
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QuoteOriginally posted by Justed Quote
Am stopping down to f8 f11 and can not afford the suggested lens...unless you are willing to take low monthly payments :-)
Long lenses magnify camera shake. Testing with hand-held shots is worthless.

If you think there is an issue with the lens, try testing it with the camera mounted on a good tripod, use the "mirror lock-up" (really the self-timer set for 2 seconds), the lowest ISO setting, and careful manual focus. Try a close subject and a distant subject. That will tell you if there is a problem with the lens.
09-06-2007, 09:44 AM   #12
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QuoteOriginally posted by GaryML Quote
Long lenses magnify camera shake. Testing with hand-held shots is worthless.

If you think there is an issue with the lens, try testing it with the camera mounted on a good tripod, use the "mirror lock-up" (really the self-timer set for 2 seconds), the lowest ISO setting, and careful manual focus. Try a close subject and a distant subject. That will tell you if there is a problem with the lens.
It is hard to use a tripod on flying birds...but I understand your suggestion. I still expect better results.
09-06-2007, 09:47 AM   #13
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QuoteOriginally posted by jfdavis58 Quote
Way too much pixel-peeping!
Badly warped sense of reality-little or no notion, much less understanding of resolution.
Example images of absolutely no value in either illustrating the alleged problem or working toward a solution.

You might be able to post-process for a slightly better presentation, but your equipment is performing nominally.
Do not understand pixel-popping or badly warped sense of reality...I wasn't high or drunk when I took those shots...hung over maybee...but not drunk!
09-06-2007, 09:48 AM   #14
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QuoteOriginally posted by NaClH2O Quote
Justed, to make you feel better, as in "misery loves company". I have the exact same problem with the 50-200. Anything further away than about 100'/30M is sadly lacking in detail. I solved the problem (sorta) by getting a second hand Pentax K 300mm F4. They are quite reasonable, if you hunt around and they have much better resolution, not to mention being a bit faster.

NaCl(I like the 18-55 a lot and dislike the 50-200 a lot)H2O
Thanks,

Will that lens autofocus...that seems important for motion photography.
09-06-2007, 10:02 AM   #15
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I'd kinda agree with John (although maybe a bit more diplomatically-Lol). Looking at these shots doesn't show me any real issue. I would make a few comments though. The Egret(?) was shot at ISO 800 f22 and 1/350th @200mm. So these settings are going to cause issues.

1) you need to shoot at middle f stops for best results with this or most any lens. When you stop the lens down this much you get image distortion from the small aperture. Each lens has a "sweet spot" which is generally in the middle ranges. Wide open or stopped down will often be much softer.
2) ISO 800 is fine when you're trying to get more out of a dimly lit scene or get more speed out of the setup to get action shots but here you don't need it. Shoot at the lowest possible ISO you can all the time. If you ever shot in the 'good old film days' then you'd understand the vast differences from a slow speed film and a high speed film. The slower the speed the less grain and higher detail you will get in every shot. These cameras do a very good job of reducing noise at higher ISO's but when you crank up the sensitivity something is going to suffer - detail.
3) Shooting at full zoom. If you read the reviews of the vast majority of lens reviews they will almost always say that shooting at the extreme ends of a zoom will soften the images. Pull back 10-20 mm and the image will sharpen up.
Combine the above and that will most likely help fix the results you are experiencing.

Another suggestion is to turn off the camera's noise reduction for daylight shooting. Use it when you are taking longer exposures of more than 2-5 seconds and longer. Also if you want the best of your camera and lenses, shoot in RAW. Jpeg's are fine but a RAW image is sharper and has a wider dynamic range. You can sharpen and do much more with a RAW image in the computer to get the results you want. Think of it as the negative in film.

Shooting technique: learn how to use hyperfocal shooting and also depth of field as well as shoot with a tripod or monopod when you can. for high shutter speeds it's less necessary but you will see a difference when the camera is more stable. When hand held, hold the camera with the right hand in the side of the camera and cradle the bottom of the body/lens with both elbows tucked into the sides of your body and shoot between breaths. All of this will improve your shooting technique and results.

Have a read of the following:
Depth-of-field explained

Hyperfocal Distance

Shutterbug: Sharpen Your Image

A series of articles on Photozone;

Photography Techniques

and a good index of articles from the Luminous landscape:

The Understanding Series table of contents

So take some pictures of a static subject just as you have the camera now. Then set up a tripod or some other way of stabilizing the camera and adjust the camera for the best settings. Take some pictures at 75, 100 and 150mm. Compare the results and I think you'll see an improvement.
If you think this is all too much then bear in mind that these things apply to all cameras and brands including film. Of course some very expensive lenses will change some of the issues and almost eliminate others but generally the above is true for most of us.

Last edited by Peter Zack; 09-06-2007 at 10:09 AM.
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