Focus issue with EF 17-40 f/4L USM

Hi everyone,

 

I have a Canon EF 17-40 f/4L USM wide angle lens which I have been using with my 6D. However, I have recently discovered that on some pictures (especially long-distance landscape shots - i.e. focus on infinity) there appears to be a significant loss of focus but only in the left hand side of the frame. I have never seen this before and I have been unable to find any info on similar problems on the web. So now I hope someone here may know what could be happening.

 

It is fairly clear that the left side of the frame is blurry while the center and right side is okay (see attached photo ). The lens is otherwise fine. For the record I do not have any issues with other lenses including other wide angles. So it is probably not a camera-problem. It does not seem to make any difference whether "Lens aberation correction" is on or not.

 

I have contacted Canon support here in Denmark but so far no answer (they may not have any idea either)

 

It's certainly not impossible that some lens components have got out of alignment.

 

On the other hand, I've found that with very wide lenses, you have to be very aware of which focus points are being chosen by the AE/AF system. It's easy to have it blindly choose the "wrong" point.

I agree. It's possible that it is an alignment problem. However, when I click on the photo to blow it up, it's clear that the problem isn't just the left top corner, even though that is where it appears worst. For example, the trees on the center of the horizon, which are about 1/4 of the way from the edge, are not in focus, and neither is the foliage near it. Unless there is a major problem with the lens, it looks to me as though it wasn't focused at or near infinity.

The problem is clearly not the plane of focus, as the center is relatively sharp throughout the image, despite the increasing distance from the camera. IMO you pretty clearly have a lens out of whack inside, because even though the fault is apparent on both sides, the left side is much worse, and it is apparent along the entirety of the left side. You'll need to send it in to Canon unless you've an optical bench handy, and some skill w/ both a JIS0, and a disassembled lens ;) ...that, or you can sell it on ebay as 'used, seems to function fine - don't like the optical quality though' ;)

I agree. It's possible that it is an alignment problem. However, when I click on the photo to blow it up, it's clear that the problem isn't just the left top corner, even though that is where it appears worst. For example, the trees on the center of the horizon, which are about 1/4 of the way from the edge, are not in focus, and neither is the foliage near it. Unless there is a major problem with the lens, it looks to me as though it wasn't focused at or near infinity.

 

Well, regarding the lens not being focused properly I would agree that it could of course happen, but not as consistently as it did (I have a number of photos where the problem is evident). All other lenses works fine so I'm assuming that its not an operator issue ;)

The problem is clearly not the plane of focus, as the center is relatively sharp throughout the image, despite the increasing distance from the camera. IMO you pretty clearly have a lens out of whack inside, because even though the fault is apparent on both sides, the left side is much worse, and it is apparent along the entirety of the left side. You'll need to send it in to Canon unless you've an optical bench handy, and some skill w/ both a JIS0, and a disassembled lens ;) ...that, or you can sell it on ebay as 'used, seems to function fine - don't like the optical quality though' ;)

 

Thanks for the reply - this is what I was afraid off to be honest.. sending it to Canon is pretty expensive :/ I have tried to do a normal alignement and I'll see if it makes any differences. But it's beginnning to look like sending it for service is the only real option :p