Troubleshooting autofocus problems

naruse

Senior Member
I'm wondering if anyone can give me any advice on troubleshooting autofocus problems.

This afternoon I was using my D610 with an AF-S Nikkor 28-300 zoom attached. It's the lens I use for general purpose and has actually been on the camera for a few months. All was going well as usual until about half way through my walk when autofocus started playing up. The point of focus couldn't be found and the motor moves the focus ring from the infinity setting to the minimum focal range and then back every time I try to focus, regardless of how far away the subject is. Since it started doing it, it has been consistent and I've not been able to use autofocus at all.

The time between the last shot when it worked and the problem starting was only a minute or two and the camera was in my hands and turned on all the time so it didn't suffer from any knocks. It is possible that I touch something which changed a setting but I can't think of any settings which would cause autofocus to play up in this way.
 

hark

Administrator
Staff member
Super Mod
Contributor
Both the camera and the lens have switches to change between auto focus and manual focus. Toggle both of them a few times and see if that helps. Maybe you accidentally bumped one of the switches.
 

Fred Kingston

Senior Member
If the lens has been ON the camera for a while, I would suspect a connection issue. I'd take the lens OFF the camera, and inspect/clean the electrical contacts between the lens and the camera body.
 

BF Hammer

Senior Member
Do you have another autofocus lens to try on the D610? If that works it (mostly) eliminates the body. Doesn't work, body is suspect.

I like Fred's advice about cleaning the contacts and reseating the lens. General best troubleshooting of a problem is start checking the easy and cheap solutions and work up to difficult and expensive. And by easy/cheap I imply don't overlook the stupid reasons too. Try the full-auto noobie photographer mode.
 

naruse

Senior Member
Thank you all for your suggestions.
I toggled the lens and body AF/M switches. I also tried in Auto, P, A, S and M modes. There was no change.
I tried cleaning the contacts on the lens and the camera body. The last time the lens was removed was in February when the camera was professionally cleaned.
I've also gone through each of the AF modes and changed between single and dynamic focal point selection. In single point I moved the point around a bit to be sure.
In all cases the result was the same, pressing the shutter release half way led to the focus going from infinity to 0.5m and back to infinity regardless of how far away the subject was.

I then tried live view and to my surprise AF seemed to work. I tried a few subjects at different distances and it seemed to work every time. I say "seemed" only because I do not trust what I see in LV 100% and I didn't take any photos to test the focus but I assume AF functionality is no less accurate in LV than it is using the viewfinder (although I almost never use LV).

Unfortunately, switching off LV, the problem comes back. I now at least have a work-around although unfortunately, as often as not I won't be able to see LV because of ambient light levels and reflections when I use the camera.

My next step is to see whether the warranty I got with the camera repair earlier in the year is still valid and if it covers this which is not directly related to the repair (a mirror replacement).
 

hark

Administrator
Staff member
Super Mod
Contributor
Then just one more suggestion. Do you have a rocket blower? You can blow out any dust or dirt from around the AF module. You'd need to make sure your battery is at least 50% charged. You can't put the body into mirror up for cleaning unless the battery is at 50% or more. Keep the lens mount opening facing down to the floor. Don't insert the blower into the opening - keep it just outside the body's cavity. If you have a loupe, you can even look to see if any dust bunnies are down in there. This is the one I have, but there are others that are equally as good.

https://www.dslrbodies.com/lenses/lens-articles/lens-technique/tracking-down-autofocus.html
 

Needa

Senior Member
Challenge Team
When using LV the focusing takes place on the sensor this is how most mirrorless cameras focus and is accurate. On a DLSR some of the light passes through the mirror and is reflected downwards to the AF sensor so it is possible the mirror assembly is involved with the issue. I seem to remember someone having an issue with a piece of the black material from the light box blocking the AF sensor also.
 

naruse

Senior Member
Thanks for the replies.

I tried cleaning with a blower. To the naked eye, the inside of the camera was spotless both with the mirror down and up.
I also re-installed the firmware just in case (it was already using the latest version but the installer allowed me to refresh it). That didn't make any difference either.
I hadn't thought about how the focusing differs between the mirror up (LV) setting and mirror down (viewfinder) settings but Needa's post got me thinking and after carefully looking at the image in the viewfinder I've noticed that there is a faint ghosting about 1/16th of the image height above the main image. This suggests that the mirror is out of position which may in turn mean light is not hitting the focusing sensor.

This gives me hope that it might be covered by the mirror repair warranty. Regardless of that, the next step has to be to get a professional to look at it.
 
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