Current Nikon camera bodies and lenses have electrical contacts. What exactly are they used for and what sorts of electrical signalling is used? Why are there so many?
Some background to my question.
Early Nikon F-mount lenses communicated to the camera with physical couplings:
- at 7 o'clock: the original aperture-indicating meter-coupling "prong" (pre-AI).
- at 10 o'clock and at 6 o'clock black aperture-indicating ridges (AI).
- at 3 o'clock a slot to engage the pin that locks lens to body.
- just below that a machined dimple indicating linear stop-down (AI-S).
In 1990 Nikon filed US Patent 4896181 which described "a camera system … provided with terminals for transmitting information data signals [between body and lens]" this described a five contact system
The Patent is long and tedious to read but I gather that these five contacts implement a simple synchronous serial interface:
- "a" - Vdd (positive battery voltage)
- "b" - P1/P2
- "c" - SCLK (serial clock)
- "d" - SI
- "e" - Vss (common ground)
When Nikon introduced autofocus (AF), at that time they introduced lenses and bodies with these five electrical contacts (by the way, at 11 o'clock is the coupling for the focus-motor in the body that drives the lens focussing mechanism)
However, later they increased the number of contacts to seven in the body.
And (later?) to eight contacts as shown in this lens, although some contemporary Nikon DSLRs (with this kit lens) still only had seven contacts! (by the way note at 7 o'clock is the focus-motor coupling in this entry-level DSLR - stare and weep ye D3200/D5100 owners with AF-D lenses)
More recent lenses have up to ten contacts!
I wonder why you need more contacts (surely the old 5-contact serial interface can just be used for newer data)? What do the "extra" contacts do?
For comparison the Nikon 1 CX mount has twelve contacts arranged
- with spring pins in body not in lens
- at the bottom of the opening (not at top as in F-mount)
- parallel to the front surface of the camera body (not radially perpendicular)