ai-s: automatic indexing (modi

AI-S coupling is a refinement of AI and became standard on NIKKOR lenses in 1982. The diaphragm action in an AI-S lens is compatible with Nikon cameras that allow the aperture to be controlled from the camera, as is required for programmed and shutter-priority automatic exposure control. All AF-NIKKOR lenses, as well as most manual-focus NIKKOR lenses made since 1982, are AI-S.