12-24mm Back Focus: Diagnosis and repair?

[beetleboy]

Hey peeps.

My 12-24mm has been giving me the shits lately. A few weeks ago I used it on a construction site shoot (redevelopment at a shopping centre) and aside from the CA (fixed with ACR) it was scarily soft from f8-11. This is on my D200.

And that's not even my concern!! I found that processing the images from ACR with 30 sharpness (not my usual workflow) gave me acceptable results so ignored that issue. I always had a feeling that this lens was "back-focussing" (WAIT, don't leave now, just cos I said the dreaded BF words!!) but hadn't used it in a situation where it was gonna be a big problem.....until yesterday!

I had a very cool shoot of a kid playing basketball and used an orange gel so I could cool the WB and make the boring white overcast sky dark blue - sorry, tangent....Anyway, so every single shot I took with AF was soft (focussing on the kids eyes) so I switched to manual and it performed like the $1200+ lens it is supposed to be.

Sat down last night and setup a foolproof BF test - 2 VHS tapes (those big box things that they used to put movies on) and everytime I AF'ed on the front one, the back would be in focus (MF was spot on). Happens mainly from about 2-3ft + (at all focal lengths).

So..this lens is less than a year old - purchased from HK via the usual channels! Is this something to be pursued via warranty or a local repairer?

Anyone else had this issue?

And a quick apology for the post length!

[Dargan]

Concerns me as this is one my next two purchases. I am assuming this would be a warranty issue if purchased through the forum. It cant be described as wear and tear surely?

[beetleboy]

I'm pretty hopeful that it should be covered by warranty..will have to contact the supplier and suss it out. S'gonna suck to be without it for however long it takes tho.

[sirhc55]

Did this happen on your previous camera when using this lens? It may be a D200 problem with this lens

[flyfisher]

Is this lens Nikon or Tokina, other?
Cheers

[beetleboy]

Chris..good question - I didn't use it much on the D70 so will check that out. I haven't had the D70 repaired for it's issues yet but it will still work for testing purposes.

flyfisher..it is the Nikon 12-24mm f4 DX.

[johnd]

it is the Nikon 12-24mm f4 DX.

Aah, there lies your problem. That lens won't work properly on your d200. Send it to me please. I'll even pay the postage.
Cheers
John

[beetleboy]

Ah, ok John. Silly me! It's in the post but I couldn't find any boxes or anything for it so i just plonked it in with a post-it note...that's what they're for isn't it?

[christiand]

Hi Beetleboy,

from what I hear you are saying is that you get great results on the D200
when manual focussing.

Well, is there any noticable difference in the viewfinder between auto and manual focussing ?

Does the D200 like the D70 have a green light and optional beep when in focus ?

Regarding beep and green light is there any noticable difference in the viewfinder between auto and manual focussing ?

I suspect the D200 may have a problem, not the lens.

However, I am by no means qualified to give you accurate advice.

HTH,
CD

[jyt]

Hi beetleoy,

I had and still have a similar problem with my 30mm sigma 1.4
have a look at this post..it may be of help.

http://www.dslrusers.net/viewtopic.php?t=15967&highlight=

I sent my lens back to sigma under warranty, but the back focus issue was still there when it came back.

I suspect it is an issue of the body with the lens itself. one of the posters had a link to his thread which talks about making the camera adjustment yourself...but I have not gut the guts to do this yet.

good luck.
Joe

[beetleboy]

Hey Christian..

I do get great results with the 12-24 on the D200 when I manual focus. Yes there is a visible difference thru the viewfinder when AF vs MF. The little green light comes on when AF'ing but I need to focus back a snitch manually to get proper focus on exposure - so the green dot is tied with the AF which is out.

Just tried the lens on my D70 and it exhibits exactly the same problem. I'm pretty sure it's a lens issue cos my 18-70mm, 50mm and 80-200mm all work perfectly on both the D70 and D200. It's definitely the lens!

Joe - that's kind of what I'm afraid of. I get the lens calibrated and it comes back with the same problem cos it's a camera:lens issue - although then it would be a D70/D200:12-24mm issue cos the prob occurs on both cams. I'll check out that post and let y'all know what ends up happening.

Thanks for help thus far folks.

[MATT]

Not knowing the full construction of the lens, how does it have a back focus problem?

I would have thought the body took care of focus and adjusted the lens as required!!

Does it have soem tie with distance ect from the lens?

But if it has the same issues with the d70, it must be the lens... I hope it gets repaired quickly for you.

Cheers

MATT