the zunow slr, which went on sale in 1958 (in japan only), was the first 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 1954 praktina fx-a which featured 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.