lbjed Loc: New York

Could someone explain to me the difference between a Ai and an Ais Nikkor lens.

PixelStan77 Loc: Vermont/Chicago

In 1977 Nikon introduced a new system for coupling the lens to the cameras exposure system. This new coupling system was called "Automatic maximum aperture indexing" or "Ai" for short. This change did not effect the traditional Nikon bayonet mount, thus allowing Ai (and the latter AF and AIS) lenses to be fitted to older non-Ai cameras.

The AIs lens was created when the aperture mechanism of the AI lens was changed to allow automatic aperture control, with cameras such as the FA and N2000. This modification means that the aperture increments of the AIS lens can be controlled more precisely by the camera.
You can tell if a lens is AIS when:

The minimum aperture (both the main larger and smaller direct read out figures) are marked in orange i.e. F16,
A notch has been taken off the rear bayonet mount, above the lens locking notch. This allows certain Nikon cameras to detect if an Ais lens is fitted or not.

lbjed Loc: New York

Thanks for the quick explanation.

pesfls Loc: Oregon, USA

Pixle Stan is correct. Non Ai lenses will have smooth surface on the mount so it’s easy to spot the difference. Some of the newer bodies won’t work with non Ai as the body can’t tell what aperature you’ve chosen. That’s a lot of why I got a Df body, as it works with darn near every lens the made and I have several in good working order that are about 50 years old. Be careful if you’re going down the road of newer body and legacy lenses. Nikon provides very useful compatibility charts so one doesn’t goof up and break something. It’s not complex but can be tedious sorting it all out.

therwol Loc: USA

With Ai lenses, you can only control the aperture with the aperture ring on the lens. Ais allows accurate aperture control by the camera, important for shutter priority and program modes on cameras that have that option. (Pretty much every Nikon camera made after AIs was developed.)

I guess I'll mention that the Nikon FA made the above not true, but how many people are still using that camera? Basically, the camera would guesstimate the aperture with the Ai lenses and compensate the exposure if the opening wasn't exactly right. It did this by taking a second meter reading after the aperture was stopped down. So if you have that particular camera, it doesn't really matter.

nadelewitz Loc: Ithaca NY

Read up on Nikon lenses:

https://www.dpreview.com/articles/6287665194/understanding-old-nikon-lenses-ai-ai-s-af-and-af-s

https://en.wikipedia.org/wiki/Nikon_F-mount

https://kenrockwell.com/nikon/nikortek.htm

BebuLamar

The OP was asking about the difference between AI and AI-s lenses not between AI/AI-S and non AI. A modern Nikon DSLR doesn't distinguish between AI and AI-s lenses because they do not control the aperture with these lenses like the Nikon FA.

BebuLamar

Only the FA can control the aperture of an AI-s or even AI lens in S and P mode. A current Nikon DSLR does not. Either AI or AI-s lens can only work in A and M mode with a DSLR.

pesfls Loc: Oregon, USA

You’re right. I noticed later that I answered the wrong question. Don’t know how to delete it. Gave up.