AI-S lens
From Nikonians Wiki - FAQs, Photo Glossary, Good Photo Locations, Help
Manual Nikkor lenses introduced in late 1981, early 1982, with Aperture Indexing Shutter system for refinded meter coupling. Smallest aperture is orange (if not, then the lens is either AI or pre-AI). Most of these lenses have extraordinary optics, like the legendary 105mm f/2.5 AI-S. 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 P programmed and S shutter-priority automatic exposure control. All AF-Nikkor lenses, as well as most manual-focus Nikkor lenses made since 1982, are AI-S.
