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Thread: AI and AIS?

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    AI and AIS?

    Hi,

    I'm wondering what these designations mean. Do they refer to the metering? Do they mean metering is automatic and it's possible to change aperture via the camera, even if it's a manual focus lens. This is my guess coming from Pentax who have 'A' lenses which did exactly this.

    Thanks in advance for any info.

    Ben

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    from wikipdeia


    • AI — Manual focus with "Automatic Maximum-Aperture Indexing", introduced in 1977. Features a metering prong similar to the pre-AI, adding cutaways which allow ambient light to fall on the aperture ring, making the current aperture setting more visible in the viewfinder. An AI lens also includes a ridge on its aperture ring that couples to the light meter and encodes the aperture setting relative to the lens' maximum aperture. A post is also fitted to the mounting flange that encodes the value of the maximum aperture, which is used for Automatic Multi-Pattern ("Matrix") Metering on some bodies. Lenses designated AI-S, Series E, and AF all include the features of AI.


    • AI-S — The successor to AI, the AI-S specification added two mechanical features required for the automatic or semi-automatic exposure modes of the Nikon FA, F-301/N2000, F-501/N2020, and F4 cameras. First, AI-S lens apertures move linearly in relation to their stop-down levers, and this feature is indicated by a special notch in the lens mount. Second, AI-S lenses with a focal length of 135mm or longer are indicated by a special ridge on the lens mount, used by FA, F-501, and F4 to engage high-speed-biased Program Autoexposure. The development of CPU-enabled AI-P and AF lenses meant that no later cameras would require these features, although the linear aperture control of AI-S remains advantageous over the non-standardized control of AI and pre-AI lenses. The term AI-S is now commonly used to refer to manual focus lenses, although all Nikon autofocus lenses with aperture rings also meet the AI-S specification.
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    Aperture Indexed. Not sure what the S stands for, but these were later lenses.
    They are manual focus and the aperture has to be manually changed on the lens, but they will tell the camera what aperture you have set the ring to, hence the camera will be able to meter.
    The digital cameras which will meter with AI or AIS lenses are D200/300/700 and the various D2 and D3 bodys.
    Other bodies won't meter, but you can change the shutter speed and check the histogram or highlights on the screen.

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    Thanks to you both. AI might work well for a wide angle prime then.

    Ben

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    AI was also refered to by users as Aperture Indexed (street term) in addition to the official encyclopedic terms. AIS was for newer cameras as per description above.
    Pre AI lenses had also "rabbit ears" prongs on the f5.6 indicator to be able to meter, older camera bodies. This is a Nikon legacy. It tries it's best not to "orphan" the previous generation of bodies/lenses and inputs forward continuity to it's designs.
    Here is a sample of "rabbit ears" on my Nikkor 50mm f1.4 AIS

    "The greatest camera in the world is the one you hold in your hands when shit happens." ©2007 Raoul Isidro

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    Quote Originally Posted by LuzArt View Post
    Thanks to you both. AI might work well for a wide angle prime then.

    Ben
    Kiwi is one quick typist, his message was posted as I was writing mine.
    It depends entirely upon what camera you have. AI will be fine for every camera but won't meter on D90 and below. D200/D300 and better it will meter just fine.
    My first nikon was a F70 which used the aperture ring to set the aperture, and I would still be happy with that way of working. I still reckon its easier than using the command dials.

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