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06-19-2009, 10:20 AM   #1
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Something wrong with my lens? Blurry around edges

First of all, I want to humble myself in front of all of you experienced, knowledgable people. I got into the DSLR game because they take great "genuine" pictures, but I am by no means a professional photographer, which is why I'm coming to you with this question.

I'm going to Japan for two weeks in August, and since this doesn't happen all the time I want to make sure I take perfect pictures. My current camera is a K100D with the kit lens, I've noticed it blurring around the edges of the pictures for a while. The center is perfectly in focus but the farther toward the edge you go you can tell its goes out of focus. Its not terrible, and with a 4x6 picture you'd never know, but I'm sure I'm going to take pictures that I want to blow up bigger than that.

Is this something wrong with the lens?
Can I fix it or have it repaired?
Should I just buy a new lens?

Thank you all!

06-19-2009, 10:34 AM   #2
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QuoteOriginally posted by bigburb Quote
First of all, I want to humble myself in front of all of you experienced, knowledgable people. I got into the DSLR game because they take great "genuine" pictures, but I am by no means a professional photographer, which is why I'm coming to you with this question.

I'm going to Japan for two weeks in August, and since this doesn't happen all the time I want to make sure I take perfect pictures. My current camera is a K100D with the kit lens, I've noticed it blurring around the edges of the pictures for a while. The center is perfectly in focus but the farther toward the edge you go you can tell its goes out of focus. Its not terrible, and with a 4x6 picture you'd never know, but I'm sure I'm going to take pictures that I want to blow up bigger than that.

Is this something wrong with the lens?
Can I fix it or have it repaired?
Should I just buy a new lens?

Thank you all!
I think that means the focus plane is not a plane at all, but rather curved, or it might be that the 18-55mm (which i have) performs not so great at the edges and looks almost blurred.
06-19-2009, 10:39 AM   #3
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The 18-55 kit lens is known to have noticable distortion at the edges at 18mm. Please post an example for us to see to confirm if this is the case or not.
06-19-2009, 11:29 AM   #4
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How about a sample with EXIF data?

06-19-2009, 11:59 AM   #5
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I will try to post a sample, how do I capture EXIF data with the picture?
06-19-2009, 01:06 PM   #6
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There are all kinds of "blurry"; some are supposed to be there and some are not. DSLRs are great for the blur that is supposed to be there, called depth of field (DOF). It is directly related to the aperture setting used for a photo. The aperture also controls how much light is allowed into the lens.

Say you set your kit lens at 24mm. The camera can use an aperture number from f4 to f27. The lower an f number is, the wider the lens is open and the more light is allowed in. That's good, but also remember that with lower f numbers, less of the photo in front and in back of the subject will be in perfect sharp focus. That can be an effect that makes a great photo, or an annoying problem.

Here's an example of very small depth of field. I think this was f2. You can see the tip of the nose is blurry, sharpness increases closer to the eye, then the back of the head is blurry. That's because of a very narrow DOF. Probably f5.6 would have gotten the rest of the head in sharp focus.



Distance also is a factor in depth of field. When you're really close, the in-focus area may be only inches at f4. At a mile away, it might extend to the horizon.

If you post an example photo, the first thing I'd look at is your aperture setting, to see if you had enough depth of field. Another kind of blur is motion blur, where the camera or subject is moving while the shutter is open. A third kind is a focusing problem, where the camera or you did not focus on the intended sublject.

Rule out those and we get to lens problems. No lens is perfect, and the degree of perfection is somewhat related to price. The kit lens is a lot better than its price would suggest but does have issues. I have never noticed unexpected blurriness, that's why I have this last. If your lens is working correctly, its flaws are only obvious at its extremes: 18mm or 55mm and small f numbers. Backing off from those settings can help a lot, say 21mm instead of 18mm.
06-19-2009, 06:31 PM   #7
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A drop off in edge sharpness is pretty typical for most lenses. With the 18-55 at the wide end, the softness can be quite noticeable with certain subjects. If you post an example, those of us that own the lens can let you know if your problems are more severe than what would be expected.

Steve
06-19-2009, 09:49 PM   #8
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If you're focusing on something at some distance--say 300 feet, or even less--the depth of field (DOF) might not reach the areas appearing in the border and corner area of the photo. The largest part of DOF (2/3 of it and more, depending of your focal length) extends beyond the focused object, not in front of it. Try to shoot at or near the hyperfocal length (whenever you shoot a scenery--also, use smaller apertures). The hyperfocal length gives you the maximal DOF for any combination of focal length and aperture. Google "focal length," and you'll find a lot of materials explaining it as well as helpful tables.

Otherwise, as has been mentioned, a drop in quality around the edges of a picture is almost always the rule.


Last edited by causey; 06-20-2009 at 07:59 AM.
06-19-2009, 11:43 PM   #9
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QuoteOriginally posted by Damn Brit Quote
How about a sample with EXIF data?
I agree with this one...
Without seeing what you mean it could be just about anything....

BR
Peter
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