Nikon AI and AIS lenses are both F-Mount Nikon lenses that have been manufactured for use with film SLR cameras. The main difference is that Nikon AI (Automatic Indexing) lenses were introduced in 1977, while the newer AIS (Auto Indexing System) lenses were first released in 1983. Nikon AI lenses feature a mechanical aperture ring on the lens barrel which allows you to manually set the desired aperture size when taking photos. On the other hand, AIS lenses do not feature this manual control of aperture size as they rely on electronic communication between camera and lens to set the appropriate f stop automatically from information provided by the camera body. Furthermore, Nikon AI lens mount lacks a certain metal tab inside it which prevents it from being used with modern DSLRs unless an adapter is used; however, this does not apply to AIS models as they are designed for compatibility with both film and digital bodies alike.