Pentax. This was the first SLR to use the right-hand single-stroke film advance lever of the Leica M3 of 1954 and Nikon S2 of 1955. Asahi (starting with the Asahi Pentax) and many other camera makers used the M42 lens mount from the Contax S, which came to be called the Pentax screw mount. Pentax is now part of Ricoh. Miranda Orion's (later name-changed to Miranda's) Miranda SLR camera was sold in Japan from August 1955 with the launch of the Miranda T camera. The camera was narrowly the first Japanese-made pentaprism 35mm SLR. It featured a removable pentaprism for eye-level viewing that could be removed for use as a waist-level finder. Yashica 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. Zunow The Zunow SLR, which went on sale in 1958 (in Japan only), was the first japanese 35mm SLR camera with an automatic diaphragm, which stopped down to the preselected aperture upon release of the shutter. (Although this invention had been anticipated by the 1948 Gamma Duflex and 1954 Praktina FX-A which could be used with a semi-automatic diaphragm, which stopped down automatically, but had to be opened manually after the exposure.) The automatic diaphragm feature eliminated one downside to viewing with an SLR: the darkening of the viewfinder screen image when the photographer selected a small lens aperture. The Zunow Optical Company also supplied the Miranda Camera Company with lenses for their Miranda T SLR cameras. General operation of a 35 mm SLR A photographer using an SLR would view and focus with the lens diaphragm (aperture) fully open; he then had to adjust the aperture just before taking the picture. Some lenses had manual diaphragms—the photographer had to take the camera down from his eye and look at the aperture ring to set it. A "pre-set" diaphragm had two aperture rings next to each other: one could be set in advance to the aperture needed for the picture while the other ring controlled the diaphragm directly. Turning the second ring all the way clockwise gave full aperture; turn it all the way counterclockwise gave the preset shooting aperture, speeding