15-85mm Lens Blur

Hi,

I'm new here and would appreciate some help.

After having a 500D for five years, half a year ago I finally got my second lens - Canon 15-85mm. I really enjoy both the wide and medium-telephoto ranges of this lens.

However, right from the start I began noticing that in many of my pictures the right side was heavily blurred - and attributed it to me being a beginner (Thought maybe out of focus, or small DoF). I was in Zurich last week and finally got to a conclusion that this must not be the case. Attached is a sample picture which illustrates the problem clearly (notice how, when viewed 100%, the buildings on the right are really blurred).

So I made a test and took some pictures near my house with a tripod and the same parameters. Once with the usual UV filter on, once off, and once with my old kit lens.

Apparently, the UV filter had a lot to do with the blur. Yet I am still pretty sure the right side of the picture is not as sharp as it should be. The pictures are attached.

So basically few questions:

1) Do you also notice any difference in sharpness from the left side and the right side of the picture (without the UV filter)? Or is this just me being too critical? I guess lens softening should at least be symmetrical...

2) Is this normal for UV filters? Mine is this one from Hoya. Are the more expensive ones better in this regard? Or should I just go without one if I want ultimate sharpness?

Thanks.

15-85mm lens with the UV filter

15-85mm without the UV filter

18-55mm

Hi and welcome on dpr forums!

I'm no expert but as I looked through your pictures there is clearly a difference between the left (better) and right sides of the frame.

I would not attribute it to the UV filter you have. I have the same filter on my Sigma 10-20 (although a 77mm Japan made one) and it can cause some flare in contra-light situations and with street lights at night but this blur is not because of that.

The houses/trees on the left and right sides are approximately in the same distance so it is not a DOF issue. I would also like to mention that these pictures does not even show the wide open performance! If I were you I'd try it wide open, too, because stopping down to F9 of F10 (like you did) can even hide a part of the problem.

By the way my Canon 18-135mm stm has a bit of this problem, too, but I noticed it only on a few shots and notat all focal lengts. The thing I can advise you is to go out with your tripod and do an extensive test wide open at all the marked focal lenghts (lens IS off, 2sec timer, mirror lockup, etc... you know ).

Then examine the results and decide whether it worths a repair or not (repair cost, warranty?). For example my lens is adequately sharp on the blurrier side even on 40x60cm prints so I decided to use it the way it is. But it differs from case to case.

Have good luck with it!

Also, at the apertures you made those shots with an APS-C sensor diffraction will certainly be contributing some softness. I try to stay around f/5.6 or f/6.7 on crop sensors.

The problem with slower zooms is then you're pretty much shooting wide open. No real room to stop down without diffraction creeping in.

omri2 wrote:

Hi,

I'm new here and would appreciate some help.

After having a 500D for five years, half a year ago I finally got my second lens - Canon 15-85mm. I really enjoy both the wide and medium-telephoto ranges of this lens.

However, right from the start I began noticing that in many of my pictures the right side was heavily blurred - and attributed it to me being a beginner (Thought maybe out of focus, or small DoF). I was in Zurich last week and finally got to a conclusion that this must not be the case. Attached is a sample picture which illustrates the problem clearly (notice how, when viewed 100%, the buildings on the right are really blurred).

So I made a test and took some pictures near my house with a tripod and the same parameters. Once with the usual UV filter on, once off, and once with my old kit lens.

Apparently, the UV filter had a lot to do with the blur. Yet I am still pretty sure the right side of the picture is not as sharp as it should be. The pictures are attached.

So basically few questions:

1) Do you also notice any difference in sharpness from the left side and the right side of the picture (without the UV filter)? Or is this just me being too critical? I guess lens softening should at least be symmetrical...

2) Is this normal for UV filters? Mine is this one from Hoya. Are the more expensive ones better in this regard? Or should I just go without one if I want ultimate sharpness?

Thanks.

Does not look so good, looks like you have a skewed/tilted lens. In the first picture, it looks like the focus on the foreground trees is sharper on the right, but in the background its not sharp, while on the left the background is sharp. More difficult to say with the other shots, but overall I do suspect something is not right with your lens.

Try shooting a brick wall straight on, then turn the camera 180 degrees upside down. If the blurriness moves with the camera, it's the lens.

Sounds like your lens is decentred.

It's happened to several of mine (including L lenses), and your Canon service centre may have a standard charge for doing the fix, and bringing it back to spec.  (I owned a 70-300L for 2 years using it on a cropped body without problem, then I tried it on a full-frame 5D MkII, and I had it back to Canon within a week!  Now it's sharp all over.)