Pre-AI, AI and AI-S

[peter_gaunt]

<p>Excuse me being thick but how do I tell the difference between a pre-AI lens, an AI lens and an AI-S lens? According to the D7000 manual the latter two will meter on my D7000 while the pre-AI lenses will not.</p>

<p>In addition the manual states that pre-AI lenses will damage the camera so I definitely want to avoid those. Just why is this by the way?</p>

<p>There's a 135mm f3.5 lens on eBay for which I'm thinking of bidding. It would largely be for use on entirely manual extension tubes (in which case it matters not a jot what sort it is) but I don't want to damage the camera if I use it without the tubes.</p>

[bob_sunley]

<p>A quick google for Mir Nikon AI will get you some good reading on the various lens mount meter coupling stuff. also a google for AI conversion will get you a few sites on how the conversion is done and pictures showing you the difference. I'm not sure if a D7000 can work properly with a converted lens.</p>

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[Andrew Garrard]

<p>AI lenses have a chunk out of the back near the mount, on the camera side of the aperture ring; it hooks onto a finger on the camera, which is on a ring that rotates around the lens mount. When you mount the lens, it moves this ring around on the camera. Since the amount that's cut out of the back of the lens depends on its maximum aperture, the camera knows what it's using.<br />

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Pre-AI lenses don't have this chunk out of the back. This means they foul the "finger" and won't mount, unless you get them adapted (by having the chunk milled out of them). However, some cameras, like the D5000 series, D3000 series and D40 series, cut costs by not having the feeler ring on the camera - they can do this because AF (and AI-P) lenses tell the camera their exposure electronically, so it doesn't matter for modern lenses. Without the feeler on the camera, some pre-AI lenses will physically mount anyway, although I believe it's on a case-by-case basis. You won't get metering because the camera doesn't know the lens's aperture, but so long as you check the histogram, all is well. The D7000 <i>does</i> have a feeler, so pre-AI lenses don't fit.<br />

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AI-S lenses have a chunk out of the mount that tells the F4 they have a linear aperture, so rather than stopping down, metering, and exposing, the camera can meter wide open. No DSLR has the feeler for this missing chunk, so AI-S lenses, like AI ones, have to be stopped down manually before shooting. This is obviously not true of AF and AI-P lenses, but the camera knows that they have linear shutters because of the electronic connection.<br />

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I hope I've got all of that right. Basically, don't try to wedge a non-adapted pre-AI lens onto a D7000, because the feeler gets in the way, and it's this that'll break if you try to force it.</p>

[david_l3]

<p>Ai and AIS have a second row of aperture numbers in small numerals. Pre-AI do not, just the single row of numbers on the aperture ring. AIS lenses have the smallest aperture numbers painted in orange, that's the easiest way for me to tell. <br>

Converted pre-AI lenses may or may not have the second row of numbers. Nikon Service modified ones do, custom/DIY modified lenses will not. <br>

Non AI/AIS lenses will break the tab follower that rotates around the lens mount. Look at the front of the camera - without a lens - it's at the 1:00 position. <br>

I use AI and AIS lens all the time on my D7000. Don't forget to input the focal length and max aperture data for each lens in the SETUP Menu so the information appears in the exif data. </p>

[robert_hooper1]

<p><a href="http://blog.gmcamera.com/2010/05/22/identifying-used-camera-equipment-part-2-–-more-lenses/">Study this</a>. <a href="http://support.nikonusa.com/app/answers/detail/a_id/5366/~/what-is-the-difference-between-an-ai-lens,-an-ai-s-lens,-and-non-ai-lens%3F">And this</a>.</p>

<p>BTW, an AI converted Nikon lens will work in M or A mode on the Nikon D7000.<br>

Use the 135mm f3.5 only if it is AI, AI converted, or AIS.<br>

I wouldn't take a chance on those manual extension tube mounts not damaging your camera.</p>

[Matthew Currie]

<p>If by "manual extension tubes" you mean the original K-1 through 5 Nikon set, they will not interfere with the AI tab, and should be safe for that. They definitely clear the tab on my F3. K-1 clears a little better than K-2, but they both leave a little room to spare. </p>

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[peter_gaunt]

<p>Thanks for all the info. I shall investigate further. So far as the extensions tubes are concerned, I've been using them for quite while with no problems with D and M42 lenses - they're M42 thread and I use them with F-mount adaptors.</p>

[Matthew Currie]

<p>Adding to the above, if you have any doubts about the AI compatibility of a lens or accessory, you can look at the aperture ring, or whatever is in place of the aperture ring, and observe if it protrudes beyond the plane of the mounting flange. Original Nikkor lenses had enough protrusion that they would hit the AI tab. Not all third party lenses do, but one must always be careful. T mounts are usually safe, as are the K rings. The following picture shows the back side of a pre-AI lens, next to the K-2 ring, which should indicate what the difference is. Note how far past the plane of the bayonet mount the edge of the aperture ring goes.</p><div></div>

[JDMvW]

<p>Much is explained at http://www.nikonians.org/nikon/slr-lens.html</p>

[bgelfand]

<p>Here is one of the better explainations I have found about the different types of lenses:</p>

<p><a href="http://aiconversions.com/history.html">http://aiconversions.com/history.html</a></p>

<p>When I purchased my F100, I had John White convert the four lenses I had been using on my FTn. The lenses work perfectly on my F100 and continued to work on the FTn (until it was stolen). If you do purchase a pre-AI lens, I recommend him for the conversion.</p>

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