Nikon Mount Lenses...To AI or Not to AI, That is the question!

To even seasoned Nikon shooters the lens mount system was the main source of confusion when first starting to build a solid lens system.  Even recently Nikon has not made the issue any easier whith the D40 and the need for AF-S lenses.  This entry is not a solid guide to the Nikon lens mount system but I was just asked a question about whether a non AI lens will work on an Classic N2000 body. 

Here is my understanding of the AI systems:

Original F mount lenses:  These are the ones that were introduces in 1959 with the Original Nikon F system.  Most of these lenses were manufactured with the prong or "rabbit ears" on them.  The prong catches a lever in the Metered Prism Finders  also refered to as Photomic Heads in the F series SLRs. For the time this was a super advanced system for 35mm cameras as it allowed for the metering to be real time with the camera.  As you adjusted the shutter speed or aperture the meter adjusted to the new settings!

However, this system was a bit clumsy as there was an extra step or two needed to mount the lenses.  First to get a smooth mount on the camera the lens needed to be set on F5.6.  Otherwise it was possible to not make connection between the lens prong and the communication lever that  told the meter what aperture the lens is set at.  Not a big deal for most folks as it was easy to take off and try again, but if you can make it better why not.  The other step for the original f prong lenses and the Photomic heads is that you needed to INDEX the meter.  What this means is that the meter that to be told what the maximum aperture of the mounted lens was as a point of reference.  

Auto Indexed (AI) Lenses: These are the lenses that came after the F prong lenses.  What this system did was git rid of the need for the prong and manually indexing the lens mounted on the camera.  Basically Nikon replaced the metal prong with a raised tab along the side of the aperture ring.  This tab moves a spring loaded ring on the camera body to tell the meter what aperture the lens is set at. 

The problem with this is that folks had a bunch of lenses with the prong on them and no raised tab (non-AI).  Nikon could do some conversions to the non-AI lenses and replace the original aperture rings with updated AI aperture rings so that old lenses could be used on new metering systems. 

AI'd Lenses: People also found that some of the non-AI lenses with enough lip could be cut so that the aperture rings made contact with the index ring on the new bodies.  This is now know as AIing a lens.  You will see it described in KEH or eBAy as AI'd.  Be careful of these as not everybody with a dremel tool is qualified to use it.   

So to answer the original question:  Will a non AI lens fit on a Nikon N2000?  Well Yes and NO.  The F mount lens will "fit" on the camera but if the non AI lens' aperture ring puts pressure on the N2000's PLASTIC Indexing ring, it could and eventually will break the tab off the indexing ring.  This leaves your camera without a working meter system.  My advice is don't do it.  Nikon made a few cameras with a metal indexing ring like the FM and the F3.  These cameras allow the user to flip the tab out of the way of NON-AI lenses so as not to damage the camera and use Stop down metering.

Please feel free to correct, add or clean up this post!  Jason

To Describe later:

AIS lenses

AF

AF-S