YS to Pentax K Mount Auto T System

YS to Pentax K Mount Front

YS to Pentax K Mount Back

This is a YS lens mount for any camera that uses the Pentax K lens mount. It maintains the auto aperture feature of the camera. It screws onto any ys lens and then the metal tab shown is used to index the YS adapter's aperture scale to the YS len's aperture scale. This is done by attaching the tab to the lens by the two small screws and choosing one of the slots seen in the last photo to line up the aperture scales. You can see the YS adapter scales go from f1.8 to 32, the full range for YS lenses. If your YS lens only goes from f2.8 to 16, you just need to index those. These are hard to find as the Pentax K mount was introduced about the same time the YS system was fading out.


The YS mount is basically an auto diaphragm T-mount system. It utilizes the same dimensions and thread pitch as a T-mount. The point of the YS system was to have an auto lens that could be used on any auto camera with the correct YS adapter, while allowing the retention of that camera's auto diaphragm system.