Erratic auto focusing: Hello fellow Hoggers. I have a good friend, a novice to photography who is having an issue with her camera. Firstly, she has a Canon 80D with the kit 18-135mm...

AndyT Loc: Hampstead, New Hampshire

Hello fellow Hoggers. I have a good friend, a novice to photography who is having an issue with her camera. Firstly, she has a Canon 80D with the kit 18-135mm lens that also has EFS on it, if that means anything. If she zooms it out to 135mm the AF often doesn't work. If she brings it back to 18 mm and then re zooms out to 135mm the auto focus starts working again. This problem is also intermittent. She tells me this camera has never been to the beach where we all know the dreaded sand can be a killer. She does however swap a pancake lens and a different zoom from time to time. I suggested it might have to do with the pins and the contact between the camera body and lens, but didn't want to offer any method of cleaning them to her. Of course there is the option of sending it off to Canon, but as a novice she would like to avoid such an expense. Any ideas, suggestions or solutions?

Strodav Loc: Houston, Tx

More information is needed. What does “often doesn’t work” at 135mm mean. Does the camera fail to AF, or does it hunt, or just doesn’t lock and she gets blurred images? Intermittent could be anything from dirty contacts to a lens that needs repair. It could be a dirty M/AF switch on the lens and just exercising it a few times might get it to work. If it’s not accurately focusing at 135mm it could be anything from technique to camera settings.

Dave327 Loc: Duluth, GA. USA

Cleaning the contacts is pretty straight forward. Cue tips moistened with rubbing alcohol and lightly clean the contacts on the lens and the camera. If that does not solve the problem then I would send it to Canon for repair.
I hope she is installing and locking the lens properly. I have the EFS 18-135 IS USM nano and it works just fine for me.

Longshadow Loc: Audubon, PA, United States

- how many focus point in use?
- is there enough light for the auto-focus system to work?
- is there enough contrast in the subject under the focus point(s)?

My Canon will occasionally go all the way to one end and then back.
I think it might be lack of subject contrast and the system cannot detect a usable difference.

DanielB Loc: San Diego, Ca

AndyT wrote:

Hello fellow Hoggers. I have a good friend, a nov... (show quote)

I'm only going to guess based on my similar experience with other Canon lenses. 1. The lens is getting old and the USM focusing motor is going out. This happened with my old 70-200 f4L. Yes this happened on my 24-105 f4L IS. 2. I had the original 100-400 f4-f5.6L IS; this lens did not like a circular polarizing filter on it and refused to
focus. Last but maybe most important 3. Is her camera's firmware up to date.

fjdarling Loc: Mesa, Arizona, USA

I didn't see anyone mention this, so ask her to ensure that at 135mm her subject is at or beyond the minimum focusing distance for that focal length. She'll find the minimum focusing distances in her lens's user guide - maybe in the camera's user guide, too, if it covers the common lenses.
Also, as someone else already mentioned - make sure there is enough light to allow autofocus to work.

TriX Loc: Raleigh, NC

So, this lens is f3.5 on the short end but the max aperture decreases to f5.6 at 135mm, so it’s possible that as the aperture closes down at the long end, there may not be enough light to AF in marginal situations. It could also be intermittent depending on the contrast and lighting of the subject under those conditions, and as mentioned, it may also depend on the number of AF points set and what the AF is focusing on. She could start by setting the aperture at a fixed f5.6 and see if the issue then occurs at different focal lengths other than 135mm.

Jrhoffman75 Loc: Conway, New Hampshire

"She could start by setting the aperture at a fixed f5.6 and see if the issue then occurs at different focal lengths other than 135mm."

Aperture remains full open during focusing and only closes down when shutter is actuated.

dsmeltz Loc: Philadelphia

AndyT wrote:

Hello fellow Hoggers. I have a good friend, a nov... (show quote)

Hard to answer with limited information. Distance from subject, aperture setting, shutter speed, environmental issues, etc.... play a role in this.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

AndyT wrote:

Hello fellow Hoggers. I have a good friend, a nov... (show quote)

Start out by really cleaning the contacts on the lens and camera body.

uhaas2009

Start always with ease- cleaning contacts...if you zoom in and out do you feel like a bump or if you turn the focus ring you feel something unusual?

autofocus Loc: North Central Connecticut

She might want to try setting the camera to "One Shot" if not already set to that, and use the center focus point to focus on a target...can't guarantee that that will solve the problem, but it just may

TriX Loc: Raleigh, NC

Jrhoffman75 wrote:

"She could start by setting the aperture at a fixed f5.6 and see if the issue then occurs at different focal lengths other than 135mm."

Aperture remains full open during focusing and only closes down when shutter is actuated.

That’s true, I stand corrected, but the smaller f5.6 aperture at 135mm could still be the issue.

DanielB Loc: San Diego, Ca

fjdarling wrote:

I didn't see anyone mention this, so ask her to ensure that at 135mm her subject is at or beyond the minimum focusing distance for that focal length. She'll find the minimum focusing distances in her lens's user guide - maybe in the camera's user guide, too, if it covers the common lenses.
Also, as someone else already mentioned - make sure there is enough light to allow autofocus to work.

Good point!

dsmeltz Loc: Philadelphia

Still can't help until we know what settings were used, what the situation was and seeing the actual photo with EXIF.