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Discussion in 'Lens Lust' started by AISBLE, Jun 22, 2007.



    Nov 29, 2006
    After seeing some of the great posts shot with the older MF lenses, I've decided to try and pick up a MF 85mm and I was hoping someone could explain the difference between the AI, non AI and AIS lenses. Any information on what I should look for or stay away from would be much appreciated.
  2. Functionally speaking there's little difference now between an AI and an AIS. The S part was for a few cameras - the FA for sure, and I think the F4 - to do P and S modes. Today all of the DSLRs use AI and AIS equally in all modes. (ie if they meter with AI, they also with AIS. If not, ditto.)

    The AI means Auto Indexing - which came in 1977 with the F2A. Pre-AI you had to match up a pin on the finder or body and align it in the "rabbit ears" you see on older Nikon lenses. Then you had to "index" the lens by twisting the aperture ring back and forth.

    When AI arrived, a part of the new design aperture ring transmitted maximum aperture information to the body - hence automatically indexing the lens for you. Some old pre-AI or non-AI lenses have bits of metal where later AI/AIS/AF bodies have important tabs or couplings, so it's wise to stay away from non-AI/pre-AI lenses for that reason.

    Having said that, virtually all pre-AI lenses can be "AI'ed" and thus brought up to AI specifications. Nikon used to do this, but now a guy called John White does them: http://www.aiconversions.com

    Whether a particular lens is AI or AIS occasionally tells you more about it. For example, with the 200/f4 non-Micro, the AI version has a noticeably stiffer focusing ring than the AIS version.
  3. CAJames


    Sep 6, 2006
    Lompoc, CA
    In short you want to stay away from non-AI lenses on dSLR's, they can damage the camera body. There is almost no difference between AI and AI-S lenses. AI-S telephoto lenses will try to use higher shutter speeds in P mode, but in most cases the optics are the same. You can see all the gory details at:

  4. The chemist

    The chemist

    Jul 22, 2005
    Also keep in mind ais lenses will have a smoother rotating focus ring in general. This was key to me when I was looking at some manual focus lenses. For me it was a royal pain focusing with an ai lens as the ring is not as smooth. Ais is so much quicker to focus as the collar travels much quicker with a lighter touch(in general:biggrin:) .
  5. gvk


    Jun 17, 2005
    Mystic, CT
    I would not agree with the adjective smoother. However, I concur that focus rings on the AIS lenses that I have owned turn with a lighter touch than their AI or pre-AI siblings. I never found these older lenses harder to focus though. I always felt that the additional damping provided by a slightly stiffer focus ring actually helped me stop at the desired focus point with less overshoot, particularly with moving subjects. On the other hand, I originally developed my manual focusing skills with these older lenses, so YMMV.

    Certainly, AIS, AI and pre-AI lenses all have focus mechanisms well suited for hand operation, unlike the looser, more sensitive, short turn, focus rings on AF lenses that are optimized for faster motor driven focus.
  6. Should you decide on a MF lens, pick up a Katz Eye screen. I have one for my 2 series cameras and I can tell you it's far more accurate than the green conformation light. An absolute must for MF IMO.
  7. If you're planning to use MF lenses on DSLR, stay away from non-AI lenses because they can damaged the body. My friend mounted a non-AI lenses on his D2X, as the result, the body wouldn't focus and meter with any AF lenses. Nikon charged $450 to fix the body.

    I would recommend you to buy AI-s lenses if possible. Why?

    1. If you use Nikon FG, FA, N2000, N2020, the AI-s lenses will allow those body to set high shutter speeds when using P mode.
    2. Sometimes the AI-s lenses have better optics. For example: the 28mm f/2.8 AI has 7 elements in 7 groups, while the AI-s version has 8 elements in 8 groups, focuses down to 7 inches with CRC.
    3. AI-s lenses are more beautiful than AI lenses :) 
  8. I am a newbie to the mf lenses for my D200 and D70 DSLRS. Just bought a 200 1:4 ai lens and am difficulty focusing. Also just acquired a 28 mm 1:2.8 ai-s lens and the focusing was a breeze. Any learning curve observations will be greatly appreciated. Is the problem with my vision (being 68 yrs with corrected 20./20); my technique, the D200's focus screen???? I am reluctant to go the Katz Eye route if the only rationalization is for using a MF lens. Your thoughts...and thank you!
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