the yashica company introduced its own slr in 1959, the "pentamatic", an advanced, modern 35mm slr camera with a proprietary bayonet-mount. the pentamatic featured an automatic stop-down diaphragm (offered only with the auto yashinon 50mm/1.8 lens), instant-return mirror, a fixed pentaprism, and a mechanical focal-plane shutter with speeds of 1-1/1000 second, along with additional interchangeable lenses.