Nikon LENS TYPE SIGNAL system

- Lars Holst Hansen

NIKKOR 35mm 1:2 (AI-S), showing LENS TYPE SIGNAL NOTCH	A LENS TYPE SIGNAL NOTCH indicates that a lens has a standardized aperture stop down action.
TC-14B, showing LENS TYPE SIGNAL PIN	An AI-S type tele converter will even relay the existence of the LENS TYPE SIGNAL NOTCH to the camera. A spring loaded pin (analog to the LENS TYPE SIGNAL PIN of an AI-S sensing camera) goes through the TC and will block out the LENS TYPE SIGNAL NOTCH on the rear side of the TC - thereby pushing in the LENS TYPE SIGNAL PIN of the camera (see below).
TC-14B, showing LENS TYPE SIGNAL NOTCH with relay mechanism	The rear side of an AI-S type teleconverter has a LENS TYPE SIGNAL NOTCH that can be blocked out by the relay mechanism pin

Only four 24*36 mm SLRs have a LENS TYPE SIGNAL PIN:

FA, F-301, F-501 & F4

Therefore only these will distinguish between an AI-S type lens and a non-AI-S type lens (a pre-AI, AI-modified or AI lens).

The APS cameras Pronea 600i and Pronea S also have a LENS TYPE SIGNAL PIN.

So why do lenses have standardized aperture stop down actions? See the AI-S type lens compatibility chart!