AI and AIS manual focus Nikkors communicate aperture preset ring position with F, F2, and Nikkormat bodies via the meter coupling prongs (“gunsight”) on the outside of the aperture preset ring on the lens. This connects to the meter coupling pin on the body or finder.

AI and AIS lenses communicate with AI, AIS, and AF bodies via the shoulder of the meter coupling ridge cut into the rear of the aperture preset ring. This connects to a rotating ring about the lens mount.

Some folks have the correct “shoulder” machined into the rear of the preset ring on original F-mount (“non-AI”) lenses to give the older lens AI compatibility.

Thus, you can use most AI or AIS lenses on any Nikon F body. The only exception is that the PROGRAM cameras, such as the FG, FA, and others require the signal notch of AIS lenses cut with the periphery of a thin milling machine cutter into the rear surface of the lens mount at one of two different depths signifying:

1. Lens is less than 135mm (or if it is a zoom, its maximum focal length is less than 135mm). In this case the spring-loaded plunger switch of the body will instruct the camera to use the low speed program up to a certain range of light levels.

2. Lens is 135mm or greater (or if a zoom, its maximum focal length is 135mm or greater). In this case the different depth of the “S” (maximum focal length Signal notch) will instruct the camera to switch to high speed program at a lower light level to avoid blurred shots from slower shutter speeds.

The Series E (“Economy”) manual focus Nikkors have no meter coupling prong and so can’t communicate with the meter of F, F2, or Nikkormat cameras.

Other than the restriction on PROGRAM bodies, you can use and AI or AIS lenses on almost any Nikon manual focus body and the position of the aperture preset ring will be communicated to the meter.