My Nikon 35mm 1.8 AF-S isn't focussing properly anymore

alexthecheese

alexthecheese

alexthecheese

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I noticed this a while back but I haven't used my camera for a good while, so kinda forgot about it.

Went out the other day with it and I can tell that it is backfocussing (I think?). It's not focussing where I need it, it's focussing behind. It's noticeable on f/1.8, but disappears by f/4 presumably because the depth of field is that much greater.

I use a D5100 so I don't expect that I can manually adjust the focussing to compensate, but I am thinking that it being quite a cheap lens it's not going to be worth fixing, or possible to fix at all? It was only £110, second hand.

Shame really, it's quite a nice little lens.
 
Or, is it my camera?

http://www.dpreview.com/forums/thread/2696677#forum-post-33683413

As you have no focus problem using live view, where the mirrors are not in the light path, but do in normal focus, where the mirrors play a roll in AF, I think your problem may be the alignment of the mirrors.

You said in your OP that the problem was not with the camera, but with the lens, as other lenses were OK. However, I suspect the problem is just not as noticeable with other lenses as with the large aperture, small DOF of the 35mm f/1.8.
Click to expand...

Quite possible. My camera has taken quite a lot of punishment in its short life. :p
 
The only way to test if it is the camera or the lens is to test multiple lenses. Unfortunately since the focus error is small it will disappear at smaller apertures so you will want to test another fast prime ideally but you can try with a slower lens like a kit lens.


The fact that the lens focuses fine with live view doesn't tell you it is a camera issue, could still be a lens issue.

Cameras commonly have the AF sensors out of alignment which will affect all lenses, but often the issue lies with just a lens. You will also find that different lenses may react differently on different cameras.

Every camera and lens is built within some tolerance, say +- 5 units (where a unit is some fraction of a mm). If your camera is -4 units and your lens +5 units (total delta of 9) then you will likely have focus issues, but if the camera was say +1 and your lens -3 (total delta of 4) then that should be small enough not to cause an issue. So sties you might get a camera at -5 u it's and a lens at -4 (delta 1) and there would be no issue except in the future if you buy a Nother lens that might be +4 for example.

These tolerance values are likely Gaussian distributed so there is a much higher chance that the errors are close to zero than at the extremes so it comes down to bad luck where you get a combo at the extreme limits in oposite directions.



Typically without micro adjust you will have to send your lens and body to Nikon for free servicing a if under warranty.
 
I don't think it does let you fine tune - Google suggests otherwise and I can't find it in the menus.

Wondering what to do. Getting the lens fixed is going to be worth more than the lens itself, as I'm not under warranty.
 
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