Lets solve the F6 digital back mystery

Started Nov 6, 2004 | Discussions thread
Joseph S Wisniewski Forum Pro • Posts: 34,130
The AF-S contact mystery...

ib1yysguy wrote:

Also worth mentioning is the 11 pin contacts on AF-S lenses while
Nikon cameras up to this point only have 8 pins in the bayonet
mount. What are the extra contacts going to be used for, I wonder?

There are 10 contacts on an AF-S lens. Looking at the back of the lens, the first seven contacts are labled, counterclockwise, with the letters A through G. I assume the other three are H, I, and J, although in lettering contacts it's common to skip I, so they might be H, J, and K.

I'll use A-J for this discussion.

The first 7 are the second nikon autofocus contact system introduced with the N2020.

A - VCC (power)
B - RW or H/S (read/write)
C - LCLK (serial clock)
D - LIO (serial data)
E - not connected
F - not connected
G - PGND (ground)

The original communication protocol, logic levels, and basic message set are described in US patent 4896181.

(The first Nikon AF system, introduced with the F3AFm which predates the Canon EOS system, for those interested, put different signals on these contacts).

These same lines are used for AF-S lenses. The AF-S lens increases power:


Adds another serial interface for teleconverter to lens communication

E - RW2
J - LIO2

Pin B becomes RW1, instead of just RW.

The AF-S focusing serial protocol is described in US patent 5727241.

The teleconverter communication protocol on pins E, I, J allows the teleconverter and lens to communicate. The teleconverter gets the "easy" part of the dialogue. It has a little processor that just says to the lens "I'm a 1.4, 1.6, 1.7, or 2x teleconverter". The lens has a bigger processor and uses the fact that it's connected to a teleconverter send a bunch of altered parameters to the camera. Min and max f stop, min and max focal length, and recommended focusing rate are all changed to reflect the teleconverter.

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