Focus Shift / Front Focus

[45tim]

Hello Gentlemen,

i bought a used Nokton Classic 35mm F1.4 SC. It looks absolutely mint. Unfortunately using it with my Leica M Film Bodies it appears to have a pretty strong front-focus problem, especially wide open. As for the attached Picture, i focused on the tin can.

I will try to have it send back and get my money back. In case the Seller will not take it back, do you guys think it can be repaired, if so, what kind of money would have to be invested for repairs.

Also what are the chances i get a Lens with focus shift if i decided to buy a brand new one?

Regards,
Tim

 

[rick oleson]

Wow, that's WAY off!

With a rangefinder camera, the focus accuracy is a function of the position of the rangefinder coupling cam at the rear of the lens, as well as the positioning of the lens cells within the barrel. I would guess that this lens must have been disassembled for service, and at reassembly either the cam was adjusted incorrectly (can happen pretty easily in non-50mm lenses) or some spacer shims were misplaced in the lens block assembly, or possibly both. I would send it back and insist on a full refund, this is repairable but I can't say what it would cost. The chances of a new lens having this problem are virtually zero.

(I should note that I am assuming here that your M body is known to be correctly adjusted; this problem could be in the camera body as easily as in the lens.)

 

[john_s]

If your other lenses focus accurately on the body, the lens is faulty and you must get a refund. Lots of lenses are bought, tested, then sold if they're not quite right. At least in this case, the fault is gross so that makes it easier to convince the vendor.

Also, I wouldn't call it focus shift. That term refers to a change of focus as the aperture is altered and is a characteristic of the design of a lens. What you have is a lens that for some reason is badly adjusted.

 

[Raskolnikov]

I have the same problem with the 90mm on my M2. All other focal lengths focus accurately, but the two 90mm lenses that I own are way off (get's worse when closer to infinity). I had the lenses checked, but they were fine. Could be problem is in the body. I would advise you to see a repairman before you return the lens.

 

[sevo]

Focus SHIFT would be when the focus is inconsistent across different apertures (or distances). This usually is a design issue which cannot be repaired. If the lens is consistently front-focusing, that is not shift, but simple misalignment - which would be easy to repair.

 

[45tim]

Thanks alot for taking the time to you all.

The seller accepted a return (ebay) and the lens was delivered back to him yesterday. Im now waiting for the refund.

I was able to test the lens on two different Leica M2 Bodys that have both been serviced < 18 Months years ago. I believe the focus if shifting throughout the apertures range but maybe its just the changing dof.

Hope to have my money back soon and will most likely just buy a brand new one and stay confident.

 

[45tim]

I have the same problem with the 90mm on my M2. All other focal lengths focus accurately, but the two 90mm lenses that I own are way off (get's worse when closer to infinity). I had the lenses checked, but they were fine. Could be problem is in the body. I would advise you to see a repairman before you return the lens.

My 35mm F2.5 Skopar focus is spot on so i rule out this option. Thanks.

 

[rick oleson]

I have the same problem with the 90mm on my M2. All other focal lengths focus accurately, but the two 90mm lenses that I own are way off (get's worse when closer to infinity). I had the lenses checked, but they were fine. Could be problem is in the body. I would advise you to see a repairman before you return the lens.

In a properly assembled lens, the cam action at the rear of the lens is identical whether the lens is a 35, a 50, a 90 or a 135mm. So, if your camera is focusing correctly with your other lenses but is off with your 90mms, the lenses are NOT fine, whatever the shop may have told you... unless all of your other lenses are bad and just happen to all exactly match each other and the body.