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AI and AIS Difference

Ben Wickerham , Jul 20, 2005; 07:44 p.m.

Was trying to establish the principle differences between Nikkor AI and Nikkor AIS lenses. For example, why a 105mm AI may be better than a 105mm AIS or vice versa. I realize this is probably a fairly straightforward question, but any help would be greatly appreciated.


Lee Hamiel , Jul 20, 2005; 08:02 p.m.

See: http://www.zi.ku.dk/personal/lhhansen/photo/AI-S-Comp.htm

This is a start - I'm sure others can be more helpful.

Regarding the 105 AI vs AIS - the AI has no built in hood whereas the AIS does.

Good luck learning all of this ...

John Newell , Jul 20, 2005; 08:33 p.m.

Technically, the answer is that the only difference in the specification is that the AI-s lenses have a linear diaphram action while the AI do not. That does not mean that there are not physical differences (e.g., the 105/2.5 mentioned) or optical differences (e.g., the 28mm/2.8 AI-s, which focuses much closer than its AI predecessor and also delivers better optical performance).

Roland Vink , Jul 20, 2005; 09:57 p.m.

Which camera do you have? As far as I know only the FA and N2020/F501 make use of the AiS features, other cameras including F3, FE and FM series treat Ai and AiS as the same.

Technically the main difference is that there is a liniear relationship between the movement of the stop-down tab at the rear of the lens and the aperture opening. Moving the tab a known amount stops the lens to a known aperture - required for accurate exposures in shutter priority and program modes. Ai and earlier lenses don't have this. However most cameras don't offer shutter or program modes with manual lenses so the feature is somewhat redundant.

A couple of cameras (EM?, FG?) do offer these modes even with Ai lenses - they set the tab to the "correct" position, then take a stop-down reading and adjust the shutter speed if necessary.

The linear stop-down is important if you have your lens "chipped" to allow metering with AF cameras. These cameras will work in program and shutter priority with CPU lenses, but the assumption is that it has a linear stop-down aperture.

A minor difference is that AiS lenses will automatically trigger high speed program mode with the FA and F501 if the focal length is 135mm or longer.

Optically, most Ai and AiS lenses are the same - same glass, same NIC coatings. The notable difference is the 28/2.8, the AiS version has CRC and is a much better lens. Very recent AiS lenses have the newer SIC coating.

AiS lenses tend to have a shorter focus movement - this allows for quicker focusing at the expense of precision.

Ben Wickerham , Jul 20, 2005; 10:01 p.m.

I personally have the Nikon FG

John Williamson , Jul 21, 2005; 02:38 a.m.

Link to how each camera can or can not utilize the AIS features. Check out the FG row.


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