I recently purchased a Nikon D5000 body for use in a very specific application. I am trying to find an inexpensive 35mm or 50mm lens for it. I do NOT require any functionality beyond that provided by a pre-CPU lens. I just need to focus on a stationary point and take pictures repeatedly. It seems that a non-AI lens would more than suffice for my needs, however I cannot find a definitive answer as to whether I can use one on my D5000. There are many that say that there is no problem using a non-AI lens on the D5000 and even that it is one of the few Nikons that is meant to allow you to do so, yet it says in no uncertain terms in Nikon's paper explaining which lenses you can use that non-AI lenses are unable to be used with a D5000.

Down at the bottom it states "The following non-CPU lenses are incompatible:" and underneath that it says "Non-AI lenses"

After typing that just now I noticed that it says non-CPU lenses; does this mean that there are CPU non-AI lenses and that I should be able to use those? Non-CPU lenses are something like pre-1980's, correct?

From what I have been able to determine from my research, it all has something to do with aperture rings and the lens physically hitting the shutter in the body? I apologize if this has been answered before; I didn't find anything when I searched but I find it hard to believe this question has not been asked previously. Thank you in advance for your help!

Edit: Well, for me this question has been rendered moot, as I've realized that I can get a Nikon DX VR AF-P NIKKOR 18-55mm f/3.5~5.6 G lens for $50 and that should work just dandy. However, I have a number of pre-AI Nikon lenses so when the D5000 arrives, I will probably post an answer here if there is not already one posted by someone else. I understand that it is probably not possible to say "all non-AI lenses work" or "don't work" because apparently some will attach to your body yet end up damaging it but it would be nice to have a rundown of what makes a lens one that you may safely use. If I suss it all out before there's an answer posted, I'll make certain to post it here.

  • 1
    Your D5000 will not be compatible with AF-P lenses. The first body in the D5x00 series that has limited compatibility with AF-P lenses was the D5200 (with the latest firmware update). Here's a link to an obscure Nikon page that lists which bodies can use which types of lenses.
    – Michael C
    Aug 9 '20 at 23:21
  • OH CRAP. Dang it, I really agonized over ordering that lens but what I found pretty much SAID that it would work. Thank you for the link to that page; imo just that link is the best answer to my question yet.
    – Ron Kyle
    Aug 10 '20 at 0:02

The AI stands for Auto Indexing, which means there is a movable ring just outside the mount with a tab on it which allowed mechanical lenses to communicate to the body the maximum aperture of the lens. With some Nikon digital cameras, that ring is still there - to make it easier to use AI manual focus lenses. But the older pre-AI manual focus lenses aren't designed around that ring (using a different, slightly more complicated system) and can break the tab on the camera's indexing ring.

Other Nikon digital cameras won't have this ring, making them less compatible with the AI lenses, but more compatible with the pre-AI lenses. Metering might not be available, of course.

My understanding is that the D5000 is one of the ones that will mount, but not meter with a pre-AI lens.

And yes, as far as I'm aware both pre-AI and AI lenses are all non-CPU lenses.

If you trust Ken Rockwell, here is a compatibility chart (that also has links to descriptions of the different technologies):


  • Thanks, I just found Ken Rockwell's site a little bit ago. Thanks for the explanation of the ring; apparently the tab breaking is why Nikon won't go ahead and say pre-AI lenses are compatible, even though it only happens with some of the pre-AI lenses. Or so I've heard. :)
    – Ron Kyle
    Aug 8 '20 at 20:58
  • Confusing the issue is that some percentage of pre AI lenses were converted to AI later, I don't know but imagine that Nikon just felt that saying these lenses weren't compatible was the safest advice they could give. Aug 12 '20 at 13:42

Pre-AI lenses require a mechanical modification to become compatible with modern Nikon cameras. You can find tons of non-AI lenses reftrofitted to new Nikon cameras on Ebay. Or you can modify the lens yourself if are inclined to, it's not very hard.

However, neither metering nor automatic aperture will work with AI/non-AI lenses on modern cameras. I have such a AI lens and have to switch to the manual mode to use it on my D3100. Apart from that, it works like a charm.

In general (my opinion), old lenses don't worth it. There is a big chance of fungus living inside and the optics evolved quite a bit since 1980s. True, those lenses are often cheap and built like a tank, but they are often several times heavier than modern alternatives. I had some fun playing with 300mm f/4-5.6 AI prime lens but then I felt that my back can't take it anymore :)


Nikon has always said non-AI lenses are incompatible with their digital cameras, due to risk of camera damage occurring if we try. I think there are cases that no damage occurs, but it seems foolish to simply walk into that known problem with an expensive camera. If that's your choice, so be it and good luck, but I'd certainly look for a later used lens.

I think AI started 1977 and CPU lenses (the first D lenses) was 1992. Newer lenses no longer say D, it is assumed now.

  • Well, I got the body for $49.99, so it's not THAT much of a risk, really. However, my question may be moot, as I think I have found AS-F lenses that are around $50 and I'm currently working on confirming that they will work with the d5000. Thanks for the answer!
    – Ron Kyle
    Aug 8 '20 at 20:02
  • Your D5000 will not be compatible with AF-P lenses. The first body in the D5x00 series that has limited compatibility with AF-P lenses was the D5200. Here's a link to an obscure Nikon page that lists which bodies can use which types of lenses.
    – Michael C
    Aug 9 '20 at 23:20

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