Nikon 300 2.8 AFS Front Focusing Errors after Servicing

Discussion in 'Nikon' started by andre_noble|5, Nov 20, 2011.

  1. Hello, Nikon Service kindly serviced my Nikon 300 2.8 lens including replacing a glass element.

    The service order lists:

    Replaced Lens Element

    Replaced Barrel (an inner barrel component I believe)

    Modified Flexible Printed Circuit

    Adjusted Autofocus

    Checked Projection Test

    Checked Sharpness Test

    Checked Image Test

    Testing the lens soon after receipt from Nikon revealed a pronounced front focus shift when using it on my Nikon D300. This focus shift
    was uncorrectable even using the maximum amount of the AF fine tune feature inside the D300's body. They clearly did something

    (I originally sent Nikon a letter insisting the lens be as optically stellar as when brand new - it appears that it is - stuff that is not supposed
    to be in focus is amazingly sharp).

    I will send the lens back to Nikon El Segundo (this is its fourth trip for related issues). 

    But I first wish to pick the brains of the knowledgeable people on this forum so I help Nikon:

    I want this lens repaired to focus accurately wide open on the D300, but I also want it accurate focus wide open on my nikon N90s and
    F100 film bodies which do not have auto focus fine tuning feature.

    What should I ask Nikon do with this lens to assure it remains optically stellar, focuses accurately on film and digital bodies?

    FYI: It focused accurately before I sent it to Nikon. In seven years of mild use it produced stellar negatives, slides and files.

    Thanks in advance for any knowledgeable input. Andre
  2. Your best option is to send all three bodies in with the lens. That's what they alway suggest when you talk to them about focusing issues. I wouldn't say they necessarily did anything wrong, it could just as easily be the d300 that's out of spec.
  3. Definitely send your camera bodies in along with your lens. They will calibrate the cameras to the lenses. This happens with all cameras that use phase detect autofocus, which is all DSLRs. The other way of doing things is contrast-detect autofocus, which cameras like the Sony NEX or your cellphone camera use (basically, if it uses live view before the shot).
  4. My D300 was calibrated fine with respect to my 300 2.8 AFS before they "adjusted autofocus" on the lens somehow. If they calibrated the
    300 afs lens to my bodies (or vice versa?), will my camera bodies then be out of whack with repect to my other Nikon lenses?

    Seems like a slippery slope. What do you recommend I do?

    Thanks for your input guys.
  5. I see your problem Andre. Do all your other lenses work OK with your D300? As far as I knew, the way the camera sees all CPU fitted lenses is unique. That's why 'lenses' have profiles stored in the camera. Now, if Nikon move the goal-posts, all of those fine-tune profiles will be wrong.
    If fine-tune can't get the lens back in focus, they have messed up. It's all very well saying 'Send your bodies in', but there's a limit to sending in ALL your AF stuff, lenses included. That CANNOT be right.
    I guess it doesn't focus right on your other bodies wide open now? The only changed variable here is the set-up of the 'fixed' lens. It's not within reasonable calibration if it can't fine tune: especially as your other cameras don't have it and they used to be fine!
    By using magnified 'Live View' to focus, can you tell how far out it is? Alternatively using plain old viewfinder MF, can you take 2 shots, one camera spot AF, one MF and feel/see how far the barrel has to go between the 2 points?
  6. Neither Nikon or Canon calibrate specific user bodies to specific user lenses. Lenses are checked on a reference body and bodies are checked with reference lenses. (You don't have to believe me; download a Nikon service manual for a lens and a body.)
    If you can, try using the lens on another body to make sure its behavior is consistent across different bodies. If you can shoot both bodies at the same objects, and the focus is different, I would send in copies of the files along with the lens.
  7. My Nikon 85 1.8 AF D seems to auto-focus accurately with the Nikon D300 body. All of my other Nikon bodies are film bodies, and I have not checked the 300 AFS 2.8 on those. I don't see the reason to:
    The 300 2.8 was fine on the D300 body before servicing, and it is so far out of AF calibration on the D300 that it can't possibly focus accuately on my N90s or F100 bodies. Does this seem reasonable?
  8. It's perfectly reasonable. What is not reasonable is this:
    I will send the lens back to Nikon El Segundo (this is its fourth trip for related issues).​
    Poor support and service is simply not acceptable. Nikon spends around 50 years establishing a high quality brand name and then can't get an expensive lens working right? No excuse.
  9. I talked to a Nikon tech rep a few moments ago, she disagreed: She suggested I test the 300 2.8 AFS lens on my film bodies - the reason being that the Nikon D300 and film bodies use different AF technologies - and my 300 2.8 AFS lens is an "older AFS lens using older technology and algorithims than the newer G lenses", so the lens may focus OK on the film bodies, but not on the D300. (I doubt that the lens will focus properly on the film bodies, but will try anyways).
    Nikon would prefer to pay for 4 shipping and 4 services rather than allow us to speak with repair reps directly.
    THAT is the problem.
  10. My two cents: Either the lens had significant aberration (significant enough to cause focus shift between the AF measurement aperture and the picture taking aperture) before the repair, and that focus shift compensated an AF sensor misalignment in your camera; in which case your camera needs AF realignment.
    OR, the repair introduced significant aberration into the lens.
    Can you test the camera with a faster lens? Option 1 (camera still has AF misalignment) should be readily visible with a faster lens.
    Third option: When I had a AF misfocus problem long time ago, somebody here mentioned that some of the higher end cameras have a selectable AF aperture; is there such a setting on the D300 (perhaps lens specific), and was it perhaps changed (for this lens)? Here is the old post regarding AF aperture:
  11. After testing further, the AF "seems" to work properly in terms of no front/backfocus.
    I need to be grateful to Nikon El Segundo for doing all this work (they replaced an early fungus-infected element, and did a full CLA) on this NON USA? lens for only $260 US total.

    Thank you, Nikon El Segundo.
  12. The focus issue reappeared with my manual focus Nokton 58 1.4 at f1.4 on the same Nikon d300 body. So it's a
    mechanical alignment issue with the Nikon D300 body.

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