Canon 7D Mk ii/100-400 ii Focus Issue: My Canon 7D Mk ii paired with the 100-400 ii lens has developed a bit of a focusing issue. I depress the shutter button halfway to initiate...

LiamRowan Loc: Michigan

My Canon 7D Mk ii paired with the 100-400 ii lens has developed a bit of a focusing issue. I depress the shutter button halfway to initiate focus, and the lens zooms in and then zooms back out to a complete blur, failing to achieve focus. It occurs on more than one focus point. It’s intermittent—that is, it doesn’t happen consistently, but happened a whole lot in my last shoot. Cause and solution anyone?

Thanks.

bleirer

I have a different Canon, but there is a camera setting that tells whether to keep searching or to stop. I believe Canon's focus by contrast, so a low contrast area like clouds or a featureless wall can give it trouble.

nadelewitz Loc: Ithaca NY

LiamRowan wrote:

My Canon 7D Mk ii paired with the 100-400 ii lens has developed a bit of a focusing issue. I depress the shutter button halfway to initiate focus, and the lens zooms in and then zooms back out to a complete blur, failing to achieve focus. It occurs on more than one focus point. It’s intermittent—that is, it doesn’t happen consistently, but happened a whole lot in my last shoot. Cause and solution anyone?

Thanks.

Is the focus-point set for single spot, or multiple/all spots, which is trying to guess on a good focus setting? Do any other lenses exhibit your problem? Could be camera doesn't know where to focus, or could be a lens issue.

How does it focus if it is set for single-spot?

LiamRowan Loc: Michigan

nadelewitz wrote:

Is the focus-point set for single spot, or multiple/all spots, which is trying to guess on a good focus setting? Do any other lenses exhibit your problem? Could be camera doesn't know where to focus, or could be a lens issue.

How does it focus if it is set for single-spot?

It is set for single focus-point. I pretty much only use that camera with that lens and have not had problems prior to last week.

nadelewitz Loc: Ithaca NY

LiamRowan wrote:

It is set for single focus-point. I pretty much only use that camera with that lens and have not had problems prior to last week.

What about other lenses?

bleirer

Try focusing zoomed in on a featureless wall maybe with the assist beam turned off to make a better test, then put a post it on that same wall. If it fails on the first but focuses on the second, I think that is normal, it is just unable to detect enough contrast. Other causes can be low light and the subject is too far away for the assist beam.

Nice article on why auto focus fails, good background reading https://www.cambridgeincolour.com/tutorials/camera-autofocus.htm

LiamRowan Loc: Michigan

Well, at the moment, the camera and 100-400 are focusing without an issue. As I noted, this is intermittent, which is making it hard to put my finger on the details and conditions. :) I'll keep trying to duplicate.

nadelewitz Loc: Ithaca NY

LiamRowan wrote:

Well, at the moment, the camera and 100-400 are focusing without an issue. As I noted, this is intermittent, which is making it hard to put my finger on the details and conditions. :) I'll keep trying to duplicate.

Do any of the contacts on lens and camera look dirty, hazy, corroded.....? Clean then with alcohol or an electonics contact cleaner or a rough cloth.

PaulR01 Loc: West Texas

Mine did that once. The focal points also disappeared off the screen. Sent it in to Canon they replaced the focal screen and one of the processors. Came back better than new.

robertjerl Loc: Corona, California

You aren't getting too close are you? I sometimes forget and do that with my 100-400L mkII and 7DII. I am so used to it being able to focus close I will forget and get down to macro distances without thinking.
Did you try cleaning the contacts in the lens and camera?
Did you check the battery(s) and their contact points, those can need cleaning also.
Finally, is it with one particular battery? It might be dying.
And check to see if something is in the mount and might be causing an iffy contact, like it turns far enough to lock but is off just a tiny bit on the contacts or even has a micro sized dust bunny in it.

Sometimes just removing and remounting a lens can clear up contact issues.

Why? Beats the hell out of me. I think Murphy just loves to screw with my computers and cameras since I am retired and he can't visit me at work anymore. Visit! he had a branch office in my classroom.

travisdeland Loc: deland, FL

You might also look to see if the focus limiting switch has been moved to a setting that prevents focusing in the length you are working in.

TriX Loc: Raleigh, NC

travisdeland wrote:

You might also look to see if the focus limiting switch has been moved to a setting that prevents focusing in the length you are working in.

Exactly my thought. There is a switch in the 100-400L to limit the focusing range (the purpose is to speed up AF), and if you’re outside the range you select, AF will be problematical. Check the switch.

robertjerl Loc: Corona, California

travisdeland wrote:

You might also look to see if the focus limiting switch has been moved to a setting that prevents focusing in the length you are working in.

I forgot all about that thing, I never use it. The AF range becomes 3 meters to infinity instead of less than 1 meter to infinity.

bluezzzzz Loc: Stamping Ground, KY

My Canon camera has a menu option "Lens drive when AF impossible." When toggled ON the camera will keep trying to focus. If OFF it will try once, out and back, and then quit trying.

Possibly your problem is related to this?

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

LiamRowan wrote:

My Canon 7D Mk ii paired with the 100-400 ii lens has developed a bit of a focusing issue. I depress the shutter button halfway to initiate focus, and the lens zooms in and then zooms back out to a complete blur, failing to achieve focus. It occurs on more than one focus point. It’s intermittent—that is, it doesn’t happen consistently, but happened a whole lot in my last shoot. Cause and solution anyone?

Thanks.

Try limiting your focus range, I believe you can set your zoom to a more narrow choice, I believe there is a two way switch on your lens, one if for full, and the other is a limiter, try using the limiter, it should help improve your focusing speed.