topic Re: Canon 15-85 - left side of image is blurry in EF & RF Lenses

Canon 15-85 - left side of image is blurry

TechSpotlight — Wed, 21 Oct 2020 04:24:38 GMT

Hello there,

I recently purchased a Canon 15-85 for my Canon T7i and noticed that some of my photos taken with this lens were awfully blurry on the left side of the image as compared to the right, and I have no idea why. Anyone have any ideas? Is there any in-camera solution I could try, or is it a defect with the lens? An example photo is shown below.

Taken at 1/800, f/8 at ISO200.

Re: Canon 15-85 - left side of image is blurry

Ray-uk — Wed, 21 Oct 2020 09:42:58 GMT

This is a sign of a decentred lens, nothing you can do with it apart from return it for repair or preferably a replacement.

Re: Canon 15-85 - left side of image is blurry

ebiggs1 — Wed, 21 Oct 2020 14:40:05 GMT

I don't know or think anything is wrong. Most lower priced plastic zoom lenses have some FL range where part of the image may get soft. Also barrel distortion can affect sharpness it too. Returning it may get you another that displays the same thing.

Re: Canon 15-85 - left side of image is blurry

kvbarkley — Wed, 21 Oct 2020 14:53:27 GMT

You seem to have this problem a lot:

https://community.usa.canon.com/t5/Lenses/Canon-18-135-sharpness-issues/m-p/264969

I knew I had seen that bus before.

BTW, the real test for testing for lens de-centering is the newspaper test:

http://www.bobatkins.com/photography/technical/lens_misalignment.html

Re: Canon 15-85 - left side of image is blurry

ebiggs1 — Wed, 21 Oct 2020 15:21:58 GMT

"BTW, the real test for testing for lens de-centering is the newspaper test:

http://www.bobatkins.com/photography/technical/lens_misalignment.html"

Great idea! Love it.

Re: Canon 15-85 - left side of image is blurry

TechSpotlight — Wed, 21 Oct 2020 15:23:53 GMT

Yes, I originally had that 18-135 and unfortunately a few months ago just after the pandemic started, I damaged it beyond repair. So I purchased this lens to use as my main walk around lens. Thanks though, I will definetely try the newspaper test when I get home to see what the results are.

Re: Canon 15-85 - left side of image is blurry

ebiggs1 — Wed, 21 Oct 2020 15:32:50 GMT

Make sure you don't confuse it with barrel distortion. These types of lenses are prone to at least some degree of distortion. And, that can not be corrected in the lens but can be edited in post by software like PS.

If a lens like the 15-85mil gets bumped or dropped even a little it can decenter its optics.

Re: Canon 15-85 - left side of image is blurry

wq9nsc — Wed, 21 Oct 2020 15:57:58 GMT

I agree with KV, you need to shoot a photo with a flat plane focal object across the width of the frame to see whether the lens has an issue.

The EF 400 f2.8 is the most expensive lens I own and I am confident it is in great optical shape but this photo shows the results when eye catching subjects are at radically different distances from the plane of the image sensor with a shallow depth of field. I suspect if you shot a scene like this one with your lens you would also find sharply focused grass across the width of the frame.

Rodger

Re: Canon 15-85 - left side of image is blurry

shadowsports — Wed, 21 Oct 2020 16:47:22 GMT

Rodger,

Agree. Here's another example of that.

85mm, f2.8, 1/200, ISO 4000

Subjects in middle of photo. f2.8 foreground and background are blurred.

Re: Canon 15-85 - left side of image is blurry

Waddizzle — Wed, 21 Oct 2020 16:54:06 GMT

I don't think there is anything wrong with the original sample shot. Nothing, at all. It is a consumer lens.

Re: Canon 15-85 - left side of image is blurry

ebiggs1 — Wed, 21 Oct 2020 18:26:24 GMT

"I don't think there is anything wrong with the original sample shot."

That was my first thought, too. I continue to think so as it is easy to confuse distortion as something more when it is not. The test will prove it.

Re: Canon 15-85 - left side of image is blurry

TechSpotlight — Tue, 03 Nov 2020 16:37:12 GMT

Thanks for the suggestions, I decided to try this with a whiteboard full of text and poiint my camera (placed on a tripod) at it. I don't think the lens is decentered based on this test.

https://imgur.com/a/nRZ1e6c

While the corners are a bit softer yes, it's not as noticable and I found sharpening it in Photoshop made it look significantly better (with the exception of the bottom right corner, which usually doesn't do that in my real world testing.)