17-40L right side corner sharper than left one?

Hi,
Two months ago I bought a used canon 17-40L and I have noticed something very strange.
When I shoot at 17mm In all my photos I can see that the left side corner is much less sharper than the right one/center, even at close apertures - F/8

Here is an example I shoot yesterday, the top image is the left side, bottom is the right.

it's certainly not normal...it sounds like a decentered element...

you probably want to send it in

I had something similar with a used 17-40 that I only noticed when I moved to FF, so I'd been using the lens for a couple of years. It was really bad on FF though.

I sent it to Canon (Irvine) and they were able to fix it, but I did have to send it back after their first attempt helped but was still not good enough. Cost ~$200. Probably means you could have bought a new one instead!

It doesnt have warranty :\
If its really that bad I can sell it and buy another one without losing much money.

I read that 17-40 isn't sharp at the corners even with close apertures, but why my copy is very sharp at the right side (same sharpness as center) but the left not so much?

TheNewLegend wrote in post #15800509
It doesnt have warranty :\
If its really that bad I can sell it and buy another one without losing much money.

I read that 17-40 isn't sharp at the corners even with close apertures, but why my copy is very sharp at the right side (same sharpness as center) but the left not so much?

I guess my question is why sell a lens to someone that you know is bad? Unless your going to get it fixed first?

best bet is to send it in to Canon and have it serviced will come back like new ..

Decentering - get Canon to collimate it

Im sure thatIf ill send it to canon the repair will cost almost like a new lens
I am still not sure if it is a real issue because I heard that the lens is not sharp at the corners even at close apertures.. Ill try to search for some information on the internet

Collimation cost is approx 3-4X a sensor clean

In Australia this means $275 AUD, so in US will probably be cheaper

But I am not from the US.
I just did a quick test and I found out that when I stopped down to f/11 the left corner turns to be much sharper than f/8
Its a little bit weird because I thought that at f/8 I get the best sharpness.

left f8, right f11.

TheNewLegend wrote in post #15802997
Im sure thatIf ill send it to canon the repair will cost almost like a new lens
I am still not sure if it is a real issue because I heard that the lens is not sharp at the corners even at close apertures.. Ill try to search for some information on the internet

the problem is you'll have a hard time selling a lens that's decentered...so it's just bad luck...better to have it fixed than not

It is definitely decentered. Either you got it as such or you did it. I did it to my 17-55 when I decided I wanted to chip off some paint from the door frame of our bathroom with the edge of the UV filter. It was a hard enough hit that the ring of the filter deformed and I have a really hard time getting it off. Was still under warranty and I brought it in with my camera, so Canon fixed it up real nice.

If you have no problem selling a defective lens, go ahead, seems like a lot of people do, knowingly or not knowingly. So far, I picked up two lenses here on POTN that had to go into service. Because of that, I will not get used again unless I can test it with my own eyes.