What are the electrical contacts on Nikon F-mount lenses used for?
Asked 6/15/2012
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Nikon F-mount lenses and bodies evolved from purely mechanical coupling to electronic contacts. Early AF-era lenses commonly used 5 contacts for lens/body communication, while later lenses and bodies appeared with 7, 8, or even 10 contacts. What do these contacts do, and why did Nikon add more of them instead of using the original serial interface for everything?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
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This blog post is by someone who wondered the same thing and got a response from someone with (apparently) detailed knowledge. In short, the number of different contact counts is due to the number of different versions of features that Nikon has included in their lenses.
The gap in the contacts in the second lens image is because the 5 contact interface was retrofitted to a design for a 7 contact interface. Those 5 pins are still all used for serial communication with the lens.
The extra three contacts on 8-contact lenses are for: an additional high power line for the lens motor, and two lens motion detection lines for direction and speed.
The two extra contacts on 10-contact lenses are for communication with teleconverters.
The response isn't sure about 7-contact lenses and speculates that they might be for lower end lenses without motion detection, but in the thread linked to by @Unapiedra a person going by the same name as the response provider in the blog post states that 7-contact lenses simply don't need the extra power that 8-contact lenses do.
The response in the post also lists what each contact in each of the 5, 7, and 10-contact interfaces is used for.
Originally by user9646. Source · Licensed CC BY-SA 4.0
user9646
14y ago
0
Generated from our catalog & community — verify before relying on it.
On Nikon F-mount, the original 5 contacts were used for electronic communication between lens and body, while older functions like aperture indexing and screw-drive autofocus were still handled mechanically.
More contacts were added as Nikon introduced new features that needed more than simple low-power data exchange. Based on the community answers:
- 5 contacts: basic lens/body serial communication and power/ground.
- 8 contacts: the extra 3 were used for newer AF lens functions, including an additional higher-power supply for the lens motor plus 2 lines related to lens motion detection (direction/speed).
- 10 contacts: the extra 2 were used for teleconverter communication.
So the added contacts were not just “more data pins.” Some were for delivering power or dedicated signals that a basic serial interface wasn’t ideal for.
Another reason is compatibility: Nikon tried to keep old lenses working on newer bodies and newer lenses working as much as possible on older bodies. Adding dedicated contacts let Nikon extend functionality without breaking the established interface.
Also note that the early F3AF autofocus lenses used contacts in a similar location but with an incompatible pinout; they are a special case and not part of the later standard AF contact scheme.
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