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jimmuller wrote:
I've been pondering the significance of "pre-AI". I'm using the FTZ so it's not so important. But I've found some inconsistencies between the written word and the reality, sort of like 'rush hour".
One video I found described how AI lenses have an indentation on the mount and orange lettering for the smallest aperture indicator.
Well then the video is wrong, and is talking about AiS, not AI The definitive sign of an both AI and AiS lenses is the presence of the smaller ADR (Aperture Direct Readout) numbers closer to the camera-mount, and the little holes in the rabbit-ears so that the f/8 and f/4 numbers will not be in the shadow of the rabbit-ears. Pre-AI lenses lack the second set of ADR numbers, and the rabbit-ears are a solid, sharp triangle. AiS rabbit-ears are rounded, not triangular, and have the two little light-holes. Also, the aperture ring will have a ridge on the side facing the camera, which engages the body's aperture following-tab: Pre-AI lenses do NOT have this ridge (unless someone used a file to add one!)
The orange smallest-aperture is indicative of an AiS lens (the follow-on to AI) but not definitive since the colour of this aperture on an AI lens _may_ be orange, or some other random colour, depending on the specific lens. What _is_ definitive of an AiS lens is that the smallest aperture number on the ADR scale will ALSO be orange. There are other external indications of AiS, but the main one is not so easy to spot: The aperture step-down lever operates in a completely linear manner (1mm of movement causes the same stop-down effect at either end of the scale), which allows accurate Shutter-priority & Program auto-exposure on appropriate bodies (e.g. FA)
jimmuller wrote:
My 300mm was described as AI-S and it has both of those features. It fits the exact description and picture from these websites:
http://www.photosynthesis.co.nz/nikon/serialno.html#top
https://www.destoutz.ch/lens_300mm_f4.5_550083.html
AFAIK it doesn't actually allow full-aperture focus with automatic stop-down on shutter release (which is what I assume AI was all about), and the FTZ doesn't seem to support it. It does have the rabbit ears for earlier full-aperture detection as per my older lenses. Obviously Nikon kept the rabbit ears to make it compatible with older bodies.
Even pre-AI lenses provide automatic-stop-down on shutter release (though the FTZ doesn't have the mechanism, so maybe that is what you are confused about?). The term "AI" refers to Auto Indexing, which means the camera automatically knows what the lens's fastest aperture is. On a pre-AI body, you had to mount the lens set to f/5.6, and then rotate the aperture fully back-and-forth to tell the body what the aperture range of the lens was.
jimmuller wrote:
My 55mm doesn't fit the description. Its f/32 mark is blue, not orange, and there is no indentation on the mount. But the SN 1033256 puts it in the last AI 105mm line of the database:
http://www.photosynthesis.co.nz/nikon/serialno.html#55Micro
and it matches the website's picture perfectly even down to the PK markings. To obfuscate even further, the Thousand and One Nights entry #85 says "With the shift to Ai, the Ai Micro-Nikkor 55mm f/3.5 was released in 1977." That spans all four 105mm AI lines in that database. So my lens would seem to be AI by both descriptions despite the lack of expected details. The rule that proves the existence of an exception, I guess. The indentation on the mount may have been an indicator to an F-mount camera but not strictly necessary for aperture actuation. The aperture ring does have a tab that actuates a small switch on the FTZ but AFAIK the camera appears not to notice....Show more →
Hmmm.. That is very strange, your Micro 55/3.5 should indeed be AI by the serial number. Possibly someone retrofitted an old pre-AI aperture ring on the lens (for what reason, I can't imagine!)
jimmuller wrote:
My F-mount Tamron 90mm Macro takes it a step further. It has an orange f/32 mark but also a lock button to keep it there, and a secondary aperture display window. If I unlock it and widen the aperture the viewfinder pops up a black screen with a note that it must be set to f/32. As with the other lenses, the FTZ works only with Aperture-priority. When I scan my slides they all report f/6.3. I can't see anything about what it is doing, not even to check DOF for a shoot. (If I want to do that with a macro I'll just use the 55mm.) But it seems to work. Another difference is the focus indicator works by turning the center metering box green, which doesn't happen with the other lenses. Clearly the FTZ isn't disallowing all lens information. But that's not MFNG and so doesn't count.
None of this matters with the FTZ but might if I start shooting film on a F body....Show more →
Pre-AI lenses are incompatible with new Nikon bodies that have an aperture follower-tab, unless they have the mechanism to flip it out of the way: The wider pre-AI aperture ring will interfere with the follower-tab, possibly even damaging it and jamming the lens on the mount. Some bodies (e.g. FM, FE, F3, Df) allow the tab to be flipped down, and can safely mount (most) pre-AI lenses. Be aware that some really old pre-AI lenses had aperture rings that were so wide they will jam on the mount.
In practice pre-AI lenses _are_ compatible with the bodies that allow them to be mounted (have the flip-down follower-tab), but you have to use stop-down metering since the body won't know what the maximum aperture is.
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Now I am done with non-ai purchases. So, here is a non-scientific anecdotal comparison between it and my ais version. Since I sold the 105mm f4 micro I added a K3 ring to each lens to bring MFD from about 40" to about 20". 5DS-R with eos-ai afapter. I'm going to refrain from my opinion, because a semi-blind old man just should do that. However, I like both and am going to keep them
I took several and this was my fave.
