Nikon didn't start as a SLR manufacturer. They produced rangefinder cameras prior to the Nikon F. The first bayonet mount Nikkor lens was produced for Canon on their Hansa Canon. Early Nikon rangefinder cameras used Contax mount and some of these Nikkor lenses were designed with a dual bayonet mount, one for Contax mount and another for Nikon's own F-mount by means of an adapter (BR-1, N-F tube). However, some of the early Nikkor lenses with the F-mount can also be used on certain rangefinder bodies.

Nokkormat FT2 105mm Auto Nikkor.jpg (22k)
A Nikkormat FT2 with an AI-modified 105mm f2.5 Auto Nikkor. Some of these early Nikkor lenses may not be multi-coated. Nikon's famed NIC (Nikon Integrated Coating) process was first seen in the Nikkor Auto 35mm f1.4 in 1971. Apart from what the lens at the back tells you, some users used the colour of the coating on the lens to determine whether the lens is an AI or non-AI.

Credit: Mr SK Hoong and Mr Poon of Foto Poon for lending their setups for me to take the images in this site.


When the
Nikon F was introduced, the Nikkor lenses for the F-mount were called the Auto Nikkor. Michael Liu has compiled a comprehensive listing of those early lenses. The F-mount allows the lens and the camera body to communicate through a lever on the camera and the lens for metering function and actual picture taking process. "Auto' means you can view the scene at the the lens maximum aperture for the brightest possible image yield in the viewfinder for easy focus, composing and metering. When a shutter release button is depressed for an exposure, the coupling lever will activate and stop the lens down (the diaphragm in the lens) to the actual picture taking aperture for an exposure. This 'automation' is made possible by mechanical levers on the lens and the camera. Early Nikon camera bodies in the professional Nikon F series (with interchangeable prisms) and the Nikkormats ( fixed Pentaprism) have metering cells either hosted in the interchangeable viewfinders (metered Prisms) or inside the fixed finder in the case of the Nikkormats. The metering cell will measure the light of a specific scene at the user selected aperture but viewing still remains at maximum aperture: this is called full aperture metering. Note: NOT ALL Nikon cameras have a metering cell, such as a basic spec Nikon F, F2 body(bodies) with eyelevel finder, Nikkorex F and the Nikkormat FS.

Here is a useful link in this site to help you understand how this communication takes place: Nikon F with the FTn Finder. (Model based on a mechanical body with a metered prism)

Nikon F Body Bareview.jpg (15k)
The Nikon F has a interchangeable finder system. There is no metering cell in the camera body. The metering is by means of adapting a metered prism to replace the eyelevel finder that came as a standard equipment or purchased directly with a metered finder. Below is a metered prism, a Photomic FTn finder designed specifically for the Nikon F.

Nikon F2A, F2AS, Nikkormat EL2, FT3 and Nikon FM in 1977 were the first batch of Nikon SLR cameras to benefit when Nikon introduced the Automatic Indexing. But first, what is indexing? Indexing is a photographic term which refers to the process of communicating the maximum aperture of the lens to the metering system for proper exposure measurement. 'Automatic Indexing' (AI) is an indexing process where it activates and engages automatically when the AI lens is mounted on an AI equipped camera. This is done by the meter coupling ridge on the outer edge of the lens mount. The Nikon F (and the cameras that followed until 1977) above does not provide automatic indexing feature on the body section. The Nikkor lenses that do not carry the projection (meter coupling ridge) behind the lens are classified as 'Non-AI' lenses.


Below are two examples set for metering in older Nikon bodies prior to the AI era:

1) A Nikon camera body that has interchangeable finder.
2) A Nikon camera body that has a metering cell built into the body.

The Photomic FTN is an example of how an older Nikon body performs metering. It takes advantage of the automatic diaphragm feature of Nikkor lenses to measure light with the lens wide open. Full-aperture metering gives a bright, clear finder image for viewing and focusing and minimizes the effect of light entering the viewfinder from the rear. In order for the meter to measure exposure at full aperture with lenses of different maximum aperture, it must be coupled with the maximum aperture of the lens in use. This is done each time the lens is attached or changed by turning the aperture ring of the lens through its entire range.

With the lens mounted on the camera, twist the aperture ring counterclockwise, then clockwise as far as it will go. This meshes the coupling prong on the lens with the pin on the Photomic FTN Finder and adjusts the meter for the maximum aperture of the lens. The adjustment can be verified by checking the maximum aperture scale on the front of the finder. The scale has a range from f/1.2 to f/5.6.

FTN Finder.jpg (12k)
For example, if the 50mm f/1.4 lens is mounted on the camera, the red index mark should appear between 1.2 and 2.8. To set the film speed, lift and turn the milled ring around the ASA film speed dial so that the red triangular index mark on the ring lines up with the number corresponding to the ASA rating of the film loaded in the camera. The film speed dial covers a range from ASA 6 to 6400. There are two dots between each pair of numerical marks for intermediate settings such as ASA 64, 80, 125, etc.

FTN finder baseview.jpg (17k)
An interchangeable metered prism.

How does a metered finder work? Early Nikon professional bodies had their metering cell on the prism (But still read light TTL). The Photomic FTN illustrated here takes advantage of the automatic diaphragm feature of Nikkor lenses to measure light with the lens wide open. Full-aperture metering gives a bright, clear finder image for viewing and focusing and minimizes the effect of light entering the viewfinder from the rear. In order for the meter to measure exposure at full aperture with lenses of different maximum aperture, it must be coupled with the maximum aperture of the lens in use. This is done each time the lens is attached or changed by turning the aperture ring of the lens through its entire range.

Lens Aperture Coupling

Nikkormat cameras reflected a different concept. They came with a fixed, non-interchangeable pentaprism. There is no such coupling as the Nikon F Photomic FTn as illustrated above. Here I am using the Nikkormat FT (the first model in the Nikkormat series) to illustrate the difference.
Nikkormat FT FrontView.jpg (17k)
The Nikkormat models (other than the FT3 and the EL2) are non-AI bodies. The FT series models (Including the AI-FT3) were the most unusual Nikon bodies because the shutter speed control and ASA/ISO are also located at the lens mount. EACH time a lens is changed, you have to reset the ASA, the maximum aperture of the lens in use for proper metering function. This was upgraded with an improved setting in the later FTn and FT2 bodies as resetting process is eliminated when a lens is changed.

Note: Nikkormat FT's metering is a full frame average metering (Meaning the meter will measure light at the whole 36 x 24mm frame and give an average metering) - the familiar center weighted metering was first employed in the FTn model. The second Nikkormat, the FS has NO metering feature at all.


Nikkormat Mount.gif (10k)
How does this Nikkormat couple with the lens for the full aperture metering ? Unfortunately, I don't have the Nikkormat FT with an older non AI lens to show you: here an AI modified lens was used instead on a Non-AI Nikkormat FT2 body. When a non-AI or AI/AIS lens is mounted on an older Nikon camera, the meter coupling pin on the body (3) or meter prism housing (Meter coupling pin - see the photomic FTn finder above) fits into the slot between the rabbit ears (4), coupling the lens to the light meter.

For Non AI lenses, mounted on a non-AI camera, the aperture ring must be set to f/5.6, and the meter coupling pin on the camera body (Nikkormats) or meter prism (Nikon F & F2) must be pushed to the right until it clicks into place. If no positive mounting is felt when moving the meter coupling pin, just push the pin as far to the right as it will go and mount the lens: the rabbit ears should fit into the middle with the pin.

Mounting A.jpg Mounting B.jpg
It is easy to identify a non-AI lens. Non-AI lenses have a solid meter coupling shoes, 'rabbit ears' on the aperture ring. Lenses with a little hole in each rabbit ear are AI or AI-S.(There are other ways for identification besides this, because some AI and AI-S lenses were designed without the meter coupling shoe). Although the E series lenses and the current AF lenses don't have such coupling on the aperture ring, but its is still possible to add a shoe on top by a seasoned serviceman. In fact, I have advised this friend of mine to convert this 105mm f2.5 auto Nikkor lens to a AI some time around the early eighties.

This then raised a question: How to distinguish a modified AI lens from an original AI lens? It is difficult, but its not impossible (See next section).

| Previous | Next | Part 1 out of 3 - Illustrating differences of AI, AI-Modified, AI-S Lenses

Back to Main Index Page

| Part I | Part II | Part III |

MANUAL FOCUS Nikkor Resources | Autofocus Nikkor Resources

Lens compatibility Chart for:
Nikon
FA, Nikon F-801 series, F-90 series, Nikon F4, Nikon F5

Back to Nikon Pictorial History Site
Back to Michael Liu's
Nikon Resources centre

Several events carried significant influence in the development of Nikon SLRs: Pre-AI (Nikon F, F Photomic, T, Tn, FTn; Nikkormat FT, FS, Nikkormat FTn; Nikon F2, F2 Photomic, F2 Photomic S, F2 Photomic SB; Nikkormat EL, FT2, ELw); AI (Nikon F2 Photomic A, F2 photomic AS; Nikkormat FT3, Nikon EL2, Nikon FM, FM2, FM2n, FE, FE2, EM, FG, FG20); AI-S (Nikon FA, F301); AF (Nikon F501, 801, F401s, F601, F601m, 801s, F401s, F90, F4 Series); AF-D (F90x onwards...)

| Message Board | for your Nikkor optics ("shared" because I want some of you to expose to other's perspective as well, it is sad to see photography has to be segmented into different camps from the use of various labels).



weblibrary.gif   Nikon F | Nikon F2 | Nikon F3 | Nikon F4 | Nikon F5 | Nikon F6 | Nikkormat / Nikomat | Nikon FM | Nikon FE/ FA | Nikon EM/FG/FG20 | Nikon Digital SLRs | Nikon - Other models

Nikon AUTO Focus Nikkor lenses:- Main Index Page
Nikon Manual Focus Nikkor lenses:- Fisheye-Nikkor Lenses - Circular | Full Frame | Ultrawides Lenses - 13mm15mm18mm20mm | Wideangle Lenses - 24mm28mm35mm | Standard Lenses - 45mm 50mm 58mm | Telephoto Lenses - 85mm105mm135mm180mm & 200mm | Super-Telephoto Lenses - 300mm 400mm 500mm 600mm 800mm 1200mm |

Nikkor Link.jpg

Index Page
  Special Application lenses:
Micro-Nikkor Lenses - 50mm~55mm -60mm 85mm -105mm 200mm Micro-Zoom 70-180mm
Perspective Control (PC) - 28mm 35mm PC-Micro 85mm
Dedicated Lenses for Nikon F3AF: AF 80mm f/2.8 | AF 200mm f/3.5 EDIF
Depth of Field Control (DC): 105mm 135mm
Medical Nikkor: 120mm 200mm
Reflex-Nikkor Lenses - 500mm 1000mm 2000mm
Others: Noct Nikkor | OP-Nikkor | UV Nikkor 55mm 105mm | Focusing Units | Bellows-Nikkor 105mm 135mm
Nikon Series E Lenses: 28mm35mm50mm100mm135mm | E-Series Zoom lenses: 36~72mm75~150mm70~210mm


MF Zoom-Nikkor Lenses: 25~50mm | 28~45mm | 28~50mm | 28~85mm | 35~70mm | 36~72mm E | 35~85mm | 35~105mm | 35~135mm | 35~200mm | 43~86mm | 50~135mm | 50~300mm | 70~210mm E | 75~150mm E | 80~200mm | 85~250mm | 100~300mm | 180~600mm | 200~400mm | 200~600mm | 360~1200mm | 1200~1700mm

Tele-Converters: TC-1 | TC-2 | TC-200 | TC-201 | TC-300 | TC-301 | TC-14 | TC-14A | TC-14B | TC-14C | TC-14E | TC-16 | TC-16A | TC-20E

Recommended links to understand more technical details related to the Nikkor F-mount and production Serial Number:
http://rick_oleson.tripod.com/index-153.html by: my friend, Rick Oleson
http://www.zi.ku.dk/personal/lhhansen/photo/fmount.htm by: Hansen, Lars Holst
http://www.mir.com.my/rb/photography/hardwares/nikonfmount/lens2.htm
http://www.photosynthesis.co.nz/nikon/serialno.html

Recommended Reading Reference on Nikon cameras and Nikkor lenses
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Credit: To all the good people who has contributed their own experience, resources or those who are kind enough granting us permission to use their images appeared in this site Note:certain content and images appeared in this site were either scanned from official marketing leaflets, brochures, sales manuals or publications published by Nikon over the years and/or contribution from surfers who claimed originality of their work for educational purposes. The creator of the site will not be responsible for may discrepancies arise from such dispute except rectifying them after verification."Nikon", "Nikkormat", "Nippon Kokagu KK" & "Nikkor" are registered tradename of Nikon Corporation Inc., Japan. Site made with an Apple IMac.