topic Re: Canon 18-135 sharpness issues in EF & RF Lenses

Canon 18-135 sharpness issues

TechSpotlight — Tue, 22 Jan 2019 02:42:57 GMT

Hey, I just bought a used 18-135 IS STM recently. Unforunately, I've ran into a problem where on the top right corner of the image, it looses its sharpness.

Here is a sample photo from the 18-135:

Compared to a sample photo from my old 18-55 IS (NON STM) lens:

In both cases, my shutter speed is at 1/1000, ISO is set to 200 and F-stop was set to f/5. Image Stabilization is also turned on. Please help!

Re: Canon 18-135 sharpness issues

kvbarkley — Tue, 22 Jan 2019 04:32:16 GMT

Was the focal length the same?

You need to post larger images.

If you "recently" bought it, it should still be under waranty, call Canon.

Re: Canon 18-135 sharpness issues

TechSpotlight — Tue, 22 Jan 2019 05:25:52 GMT

Apologies, I'll post larger versions of the image from the 18-135 below:

If you zoom in to the top right corner, you can see what I'm talking about.

And the 18-55 IS for comparsion below:

The focal length on the photo taken with the 18-55 IS was 39 mm and the focal length on the photo taken with the 18-135 IS STM was 35mm. The lens was bought used and I checked, it's no longer under warranty.

Re: Canon 18-135 sharpness issues

MikeSowsun — Tue, 22 Jan 2019 07:06:58 GMT

It does look like the lens is soft on the right side. It could be "de-centered".

f/5 is almost wide open. It might get better if you stop down to f/8. You can send it in to Canon to get checked, or just live with it.

Re: Canon 18-135 sharpness issues

ebiggs1 — Tue, 22 Jan 2019 14:44:39 GMT

"The focal length on the photo taken with the 18-55 IS was 39 mm and the focal length on the photo taken with the 18-135 IS STM was 35mm."

You have so many things wrong with your reasoning, let's start. First you can not compare two totally different lenses expecting them to both be as sharp as each other. Just ain't gonna happen. Next any smaller zoom range lens will tend to be sharper than a larger zoom range lens. A fact of life. It is the price you pay for convenience of zooming. You were shooting nearly wide ope which is the worst place for almost any lens for best IQ. Try again at a reasonable aperture of f8. The left side of the shot is closer than the less sharp right side. Lastly, although 4mm difference in aperture is small it will have an effect on the shot.

Someone above said to live with it. That is the best advice for a lens of this type because it is probably as good as it is.

Re: Canon 18-135 sharpness issues

TechSpotlight — Wed, 23 Jan 2019 17:07:51 GMT

Thanks all for your assistance. I tried stepping it down to f/8 and made the right side improve quite a lot. It's still a little bit blurry but barely noticable to my eye at all.