Asahi Optical introduced its first 35 mm camera in 1952. Unlike the majority of Japanese camera manufacturers of the time, Asahi made a conscious decision not to produce a mere German rangefinder copy, a relatively simple task. Instead, Asahi decided to copy the Praktiflex, a 1939 design, made in the German Democratic Republic. Asahi's designers (Nobuyuki Yoshida and Ryohei Suzuki) were convinced of the inherent superiority of the SLR and so proceeded along these lines. This effort resulted in the Asahiflex I, which was also the first Japanese 35mm SLR.
The Asahiflex I had a non-interchangeable waist-level viewfinder, with a direct optical viewfinder for eye-level use. The Asahiflex I had a non-returning mirror (which, however, was directly coupled to the shutter button, so only when the shutter button was released the mirror returned to the down position) and shutter speeds from 1/25 to 1/500. The camera used the M37 screw mount. The Asahiflex I went through some minor modifications for flash use, resulting in the IA.
The Asahiflex IIB was released in 1954. With the IIB, a key advance was made, the quick-return mirror. It was the world's first SLR camera with an instant return mirror. The problem of mirror black-out was one of the main problems with prior SLR designs, greatly reducing usability and leading to the greater popularity of the rangefinder. With the IIB there emerged the first practical quick-return mirror, a vital innovation and one which was quickly adopted by other manufacturers. With the final model in the series, the IIA, the Asahiflex gained slow speeds from 1/25th of a second to 1/2 of a second.