I'm having trouble with a new old lens I picked up recently, and I'm wondering if it is a K mount. It does fit on my K100D just fine, but when I power up the camera, Av just blinks on the LCD display, and the F value blinks in the view finder. It doesn't seem to matter which setting I have the camera on either.
If I compare this lens (Gemini MC Auto) to my Pentax A 50 lens, the big fin closest to the lens and the tall narrow fin are next to each other on the A lens, and about 45 deg. apart on the Gemini lens (see pic).
I'm not sure how "auto" the gemini lens is, since it doesn't have an A setting on the apature ring. Anyway, I can't get the K100D to take a picture with it. It just doesn't seem to like this lens. I gues that is why I'm questioning if it really is a K mount or not.