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  1. #1

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    Nikon 24mm F2 Ai - decentering?

    Hi folks,

    Long time no post. I have a Nikon 24mm that I had been using up until recently when some of my results came out a little... fuzzy.

    I usually shoot this lens wide open at F2 or stop down to F2.8.
    At F2, the lens exhibits a blur effect on the left and right edges of the frame. Almost like the "instagram" circular blur (where only the center portion is in focus). This is great if it's what I want but ... it's not.

    The thing is, at F2.8, most of the effect is gone except for the left side where a bit of the image turns to a blurry mess.

    Image attached for reference. I'm thinking this isn't normal for this lens?

    Click image for larger version. 

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  2. #2

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    try shaking the lens and see if anything rattles? I've had lenses where element rings get loose over time and caused similar issues. Definitely doesn't look normal.

  3. #3

    Join Date
    Dec 2006
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    You don't say old your lens is but in general, lenses can become internally misaligned with age and use.
    (I think this is more of a problem with the wider angle lenses.)
    Never could afford the 24/2 but I did have an old (about a 1980 model) 24/2.8 that made pictures about like your example.
    A trip to the shop for a CLA and re-alignment on the Nikon collimating (SP) jig and the world was all in focus again.

  4. #4

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    I have a 28mm f/2 AiS that rattles a lot when shaken laterally. That guy Rockwell says they're prone to a loosening of something in the moving CRC group. I think the 24 f/2 Ai has CRC too. Might be a similar issue. Looks like de-centering to me. Good luck and let us know how this turns out.

    s-a
    I photograph things to see what things look like photographed.
    - Garry Winogrand

  5. #5

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    Thanks for the tips folks. I gave it a good shaking but it had no rattling. Glad to know its a problem with the lens!
    Sounds like it needs a trip to the Nikon doctor... So will probably post it to them soon.

  6. #6

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    I wouldn't be too quick to send it off; I've had 3 copies of this lens and still have one, and they all basically look like that when its wide open at that distance. Its not this lens' forte, the mid to far range at wide open, where it shows lots of softening towards the edges. I would test it against a brick wall to see if the defocus is uneven, if it is even on both sides then the lens is fine.
    At mid to close range wide open and at 2.8 with the subject at the center or near it the lens does very well. This is not a landscape lens. It's a low light mid to close range wide angle, where you need to get the shot. I'm not saying that it could actually be a de-centering but all the 24mm f/2 at wide open at that distance very much look like your image.

    As for the CRC and rattle, all the 28f2's I have (2) and others that I've worked on have a bit of rattle due to the front CRC (as opposed to the 24 f2 and 2.8 with REAR CRC), the mechanism has a bit of play in it that does not shift the elements.

  7. #7

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    Had a 28 f2.8 AIS that the CRC cell had worked its way so far out that the unit wouldn't focus properly. You might check to see if you can rotate the front cell in a clockwise direction. I pushed the lens against my palm and found I could rotate it back and forth. I rotated it back into position and tightened it and all was well.
    -Fred

  8. #8
    fstop's Avatar
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    Why are you shooting a wide wide open?
    APUG: F, F/FTN,F2,F2A,F2AS,F3,F3HP,FA,FE,FM,FM2,FE2,XK,XM,XD, XD-5,XD-7,XD-11,XE,XE-5,XE-7,SRT101,SRT102,XG9,XG7,XG1,XG-SE,XG-M,X700,OM-1,OM-1n,OM-2,OM-2n,OM-4,F-1,F-1N,AE-1P,R5,500C/M,SCII
    DPUG:D100,D200,D300

  9. #9
    Newt_on_Swings's Avatar
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    I also have this lens, and it is also a just slightly loose on the front barrel. I should take it apart one day and try to tighten it. I have not noticed any image degradation when using this lens though. This type of image did occur once on my Canon Demi S when I first got it, the lens was not tightly screwed down onto the body, It is supposed to be screwed in with 4 screws, and when I opened it up, only one was on, the two others were very loose. This allowed the lens to tilt a bit if pushed.

  10. #10

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    I suggest checking the pressure plate to verify that it’s holding the film flat against the film registration rails.

    If the right side of the pressure plate wasn’t holding properly, that could account for the blur on the left side of the image.

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