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Nikon D3100 no longer auto focusing

Posted: Thu Sep 07, 2017 12:44 pm
by dunkle
I have myself a Nikon D3100 which I hardly use. Probably every few months for parties and pictures of daughter at birthday and Christmas.

I do use a prime lease (I believe that’s correct term) as it’s only really used for close up face pictures

Anyway, come to use it today for her first day at nursery and found it no longer auto focuses. I tried it with the original lens that came with it but still same

Would this be a common problem ? Easy to fix ?

Posted: Sat Sep 09, 2017 7:38 am
by ArthurDent
You do have the mode dial set to auto don't you? It's not on "M" by any chance?

Posted: Sat Sep 09, 2017 9:06 am
by Arthur Fowler
Have you tried both focusing types (traditional and liveview)?

Posted: Sat Sep 09, 2017 9:17 am
by Harold1066
Sounds like it maybe the contact between camera and lens. Take the lens off and look in, at the top on body. You should see the contacts, are they clean, not bent.

As it's two different lens this probably is the most likely cause, other than mode dial or lens set to M.

You could also try a reset to default setting in the camera, this may cure the problem.

Posted: Sat Sep 09, 2017 10:47 am
by dunkle
Certainly auto and yes in both view modes, will try the contacts and report back

Posted: Sat Sep 09, 2017 4:37 pm
by ian turner
er it auto focuses if mode dial sets to m, only if you flip the switch on the lens to manual or possibly change the setting in menus (wouldn't know as have never set to purely manual focus just m,anual on the dial)

Posted: Sat Sep 09, 2017 6:18 pm
by Harold1066
One other thing is that it could have been set to back button focus (don't know if d3100 has this) but that would mean changes in the menu settings.

Posted: Sat Sep 09, 2017 6:35 pm
by scoobyood
Is the AF lock button stuck..?

This one...

https://cdn.photographylife.com/wp-cont ... L-AF-L.jpg

Sent from my Nexus 6P using Tapatalk

Posted: Sat Sep 09, 2017 7:08 pm
by dunkle
I shall check it all Sunday once finished my night shifts and report back

Thanks for the advice so far

Posted: Sun Sep 10, 2017 8:49 pm
by Arthur Fowler
If the lens supports M/A (autofocus with manual override, MF

priority), manual focus can also be selected by setting the camera

focus mode to MF (manual focus; 0 55). Focus can then be adjusted

manually, regardless of the mode selected with the lens.

Posted: Mon Sep 11, 2017 11:02 am
by dunkle
Cheers guys

I removed the lens and ran a qtip over the contacts, putting the lens back on, it seems better, but does not seem as quick / smooth as I remember when focusing, but maybe thats just me

I know next to nothing about using DSLR, but the camera and lens combo was recommended as a way of being able take good pics of my little girl as she grew up, and that was certainly true

The lens is a Nikon AF-S NIKKOR 35mm 1:1.8G
Has the M/A and M switch

The AE-L AF-L button does not seem to do anything that I can tell
Im not even 100% certain what the best settings are in the menus

Posted: Mon Sep 11, 2017 6:19 pm
by Arthur Fowler
Doesn't sound very healthy. The 35mm lens is a beauty and should focus very quickly. It should be set to M/A on the lens.

My apparently garbled post above your last one was a copy and paste from the manual stating how you can change within the menu settings to MF which would stop the autofocus working but if it is working at all as seems to be the case then that's not your problem).

Posted: Tue Sep 12, 2017 9:00 am
by dunkle
Cheers. Both lens seem to be the same, so maybe it’s just me thinking it was “better” before

Would there be a list for the optimum menu settings in case I do have problem there.

Posted: Tue Sep 12, 2017 9:55 am
by Q
Ive got the D3200 and its had very little use. Isnt the Zoon motors in the Lenses themself?
When I was looking at 300mm Zoom lens then the Manual Zoom(as in no Zoom Motors on the Lens) were 50% cheaper than the Auto-Focus versions.

The fact that both lens dont work for you may point towards the bit in the camera that uses the Zoom Motors?

Maybe try ringing Nikon UK and see if you can speak to someone in the Service Dept?

Posted: Tue Sep 12, 2017 10:26 am
by dunkle
Is the zoom / Auto focus the same thing ?
The fixed lens does not even have option to zoom

Posted: Tue Sep 12, 2017 8:21 pm
by Harold1066
DuncanSWardle wrote:Is the zoom / Auto focus the same thing ?
The fixed lens does not even have option to zoom
No, the Auto focus motors are built into the lens.

Zoom lens ( i guess you have the 18-55mm kit lens) is manual zoom but auto focus.

On both lens when you half press the shutter button the lens should move to focus and a green light should appear bottom left in the viewfinder, if its blinking the camera can't focus.
Would there be a list for the optimum menu settings in case I do have problem there.
In the menu you can have AF-assist on, which will help with focus in dim lighting.

As you don't use the camera much, I would imagine that most of your settings are the default.

Posted: Wed Sep 13, 2017 1:52 pm
by dunkle
Cheers, just spotted the little green light, it certainly was not there previously when having issues, but now both the stock "zoom" lens and more importantly the 35mm "prime" lens has the green light and seems to be focused perfectly

Now to experiment with the settings

Posted: Tue Sep 26, 2017 11:48 am
by gibletbuilder5
The auto-focus (or phase-detection) sensor might need cleaning. It's generally safe to turn the camera off, take the lens off and lift up the mirror. Underneath the mirror will be a little window or glass rectangle. If you carefully get some sticky tape, lightly press it on that piece of glass and gently peel it back off it should clear any dust on it. This should get it back up and working. If not, take it to a service center.