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Focus Issues Bought myself a used Canon 70-200mm F4 L USM IS Lens but as yet I've not achieved a single Sharp image list of various settings tried attempts so far and still no joy very frustrating. I placed lens both on my Canon 20D & 40D still no

1,Tried faster shutter speeds & An array of F-stops (all within correct exposure) using inbuilt camera meter as well as Sekonic 758 dr 2,Live view x5 & x10 manual focus on my 40D 3,100,200,400,640 800 1600 3200 iso 4,Mirror lock up & cable release

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5  
You've told us your problem. Now what are you asking? –  Michael Clark Jun 1 '13 at 14:36
1  
If you have a filter on take it off, just had a similar problem. –  user20244 Jun 2 '13 at 13:33
    
Not disagreeing with answers given but you might try it on another camera body, a new one at a camera shop. –  Frank Jun 3 '13 at 3:42

3 Answers 3

Are all Canon 70-200mm f/4 L IS USM lenses soft? I would say no. Even on full frame this lens is considered to be very acceptably sharp corner to corner for a telephoto zoom lens. No it isn't going to give you the sharpness of a prime macro lens, but it is not soft.

Beyond noting that it is not a lens design issue. I would suggest testing the lens properly using these existing tips from other questions:

Beyond that, if you do see issues you can attempt to microadjust your lens if that is an option on your camera body, see:

If all of the above fails and it still doesn't look good, your next steps would be to send it to a repair center or Canon, preferably with a body to match it to. They can calibrate further or determine if it is defective.

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Neither the 20D nor the 40D have AFMA. The only x0D with it is the 50D. –  Michael Clark Jun 1 '13 at 21:31
    
AF calibration errors will not affect manual focusing, which is also yielding soft images. –  Michael Clark Jun 1 '13 at 21:46
    
@Michael Clark - I agree on both points. My answer was pretty quick and dirty ;) –  dpollitt Jun 1 '13 at 23:51
    
Whoa! I didn't know that the 50d was the only x0d that had AFMA. Glad I didn't sell mine! –  Peter pete Jun 2 '13 at 0:58
    
50D has about everything now that magic lantern is on it. It is a great value. –  dpollitt Jun 2 '13 at 1:08

The EF 70-200mm f/4L IS has a reputation as a fairly sharp lens in general, and a very sharp zoom lens in particular. If you are not able to get a sharp image with it you should consider sending it to Canon factory service for calibration and adjustment.

There are several issues that could be causing the problem, but the two most likely candidates are either a de-centered lens element (possibly caused by a hard impact) or problems with the IS that cause the correcting element to be out of alignment. In the case of an issue with IS, even when it is turned off it could still cause problems if the element isn't parked where it should be when not active.

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Gday.

When you check for sharpness, do you check it on the LCD of the camera? or a computer? I've tried a 40d and I find that its LCD screen doesn't have enough pixels to determine if a photo is sharp/well focussed.

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This would be good for clarification, but it is not really an answer but rather a comment. –  Michael Kjörling Jun 3 '13 at 13:33
    
True. ... sorry –  Peter pete Jun 3 '13 at 20:41

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