Difference between Nikon AI and AI-S lenses?

I am aware that AI-S is newer and that some AI-S lenses such as the 28 mm f/2.8 has a much improved optical formula with CRC compared to its AI predecessor. But what I am looking for is the technical difference between the systems.

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The main difference is that with AI-S, there is a standardised linear relationship between the movement of the stop-down tab at the rear of the lens and the aperture opening. I.e. moving the tab a known amount stops down the lens to a known aperture. This is required for accurate exposures in shutter priority and program modes. AI lenses do not do this.

In addition, AI-S lenses will automatically trigger the high speed program mode (where the camera will pick a shorter exposure time for hand-holding) with the FA and F501/N2010 if the focal length is 135 mm or longer.

However, only a few old camera models, such as the FA (1983) and F501/N2020 (1986) make use of these features. Newer cameras (including the F3, F4, F5, F6, the FE and FM-series and all digital models) treat AI and AI-S as the same. These models do not let the photographer use shutter priority or program modes with any manual lenses. For these models, the AI-S functionality is redundant (unless the lens is “chipped”).

If a manual focus lens is “chipped”, setting the aperture on the body, instead on the lens itself, only works with an AI-S lens.

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