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I bought a canon 50-250mm IS lens (for my T1i), maybe two years ago and haven't used it much, but whenever I do, I always regret using it. Pictures are blurry, the depth of field too shallow and so on. Here's an example:

enter image description here

I shot this one in auto mode, and it is awful. I can definitely see that some of the blur is from handshake, but the surrounding is extremely blurry. Is my lens broken or is this normal?

I am still learning about photography, and did get a much better shot, but I had to hop on a boat and get much closer.

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Have you tried Image Stabilisation (One of the switches on the lens)? –  damned truths May 3 at 13:00
    
IS is enabled, it still doesn't affect image quality. –  Candide May 3 at 13:28
    
Can you post more informations, such as shutter speed, ISO, focal length, etc, also known as EXIF data ? –  Andy M May 3 at 14:45
    
maybe you bought a lensbaby instead? –  Michael Nielsen May 3 at 21:58

4 Answers 4

up vote 12 down vote accepted

There is definitely something very wrong here. That's not a focus or DOF issue, but looks like the lens suffers from extremely strong field curvature.

It's normal for a lens to be sharper in the center than around the edges, and this effect gets stronger with wide open aperture and at the extreme ends of the zoom range (your last sentence indicates that you get sharper images when you zoom in less). But it should never be as extreme as what is visible on your picture, at least not in a lens produced later than 1900.

I can't think of any way that user error could produce this result. It definitely looks to me as if that lens is broken, i.e. has a strongly decentered lens element. You should have sent it back right after you bought it, but you should contact Canon's service department in any case; hopefully they will still fix it - maybe not for free, but decentered elements are usually not the "broken beyond repair" kind of problem.

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1  
It almost, but not quite, looks like the user was zooming during a slow exposure (zoom blur). digital-photography-school.com/… –  Michael Clark May 4 at 3:07
    
Hi michael. I was thinking what is a reasons for this damage. Is it due to a poor handling or is it a manufacturing errors ? –  Borat Sagdiyev May 4 at 18:52
1  
@BoratSagdiyev: it can be both. Decentering can happen when a lens is dropped, but checking whether all elements are properly centered (and adjusting them if not) is also one of the last steps in the production process and could have been skipped or done incorrectly for some reason. –  Michael Borgwardt May 4 at 20:08

The softness at the edges is definitely caused by a decentered lens. This just means one of the internal glass elements is not properly aligned with the others. Like so;

enter image description here

(It could be any of the elements...this is just an example of the far left being off.) I'd recommend that you immediately send it in for repair to Canon. You can start here:

http://www.usa.canon.com/cusa/consumer?pageKeyCode=onlineRepairLanding

You can actually find out exactly what's wrong with your lens by using a homemade star chart. Place some circular binding reinforcement stickers in an x on a black sheet of paper. You can find these at some office supply stores.

enter image description here

Take a picture of the x arrangement and zoom in on the circles. You should notice the black "bleeding" on to the edges of some (if not all in your case) the white circles. Note which direction the bleeding is occurring as this will give the direction of the offset of the misalignment.

You might mention these results when you send it in to Canon for repair. Hope this helps.

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One of the lens elements is badly decentred, send it to your nearest Canon service centre for repair.

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2  
Or keep it as a portrait/pictorialist lens, large format users love lenses with uncorrected defects. (re: Petzval lenses, lomography, pictorialism) –  Patrick Hughes May 3 at 18:45
    
Sorry Patrick, but some lenses just can't be loved and I think this is one of them. –  Kendall Helmstetter Gelner May 5 at 4:49
    
@KendallHelmstetterGelner maybe not as a lens. As a doorstop or paperweight maybe? –  jwenting May 5 at 8:21

This problem has been existent even on some macro lenses. The lens shows a "linear" (instead of circular) area as sharp and rest of the area as blur. This problem, to my way of thinking, is existent due to the lens being poorly manufactured. The second reason might be due to extreme sensitivity of the lens towards the light rays that refract all around the edges.

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