World War II had cost Japan millions of lives, and most of its industry and infrastructure was destroyed. Japan adopted a pacifist constitution with emphasis on liberal and democratic practices. In 1952, the allied occupation in Japan and in 1956, Japan was granted admission in the UN. This became the starting point for an spectacular economic growth in Japan for the next four decades. This is how Japanese SLRs came to be
Japan had been doing optics for some time then. Pentax (or Asahi, as it was then known) had military contracts for optical instruments during WWII. At the end of the war, the company was disbanded for three years, when in 1948 it was allowed to re-form.
In 1952, Asahi released the Asahiflex I, the first Japanese 35mm SLR. In 1954, the Asahiflex IIB became the first Japanese SLR with a return mirror.
By the end of the 1950’s, the SLR design was homogenized.
In May 1959, Canon introduced the Canonflex. The Canonflex featured a quick return mirror and an automatic diaphragm ("with Automatic Springback Diaphragm and Mirror"-1959 Canon Brochure). It was also the first camera to have Canon’s breech lock FD mount. In theory, the system made any mount a secure one. You only had to tighten the breech. When in practice, though, this turned out to be unpractical, since more time had to be devoted to attaching or removing the lenses. The Canon FD mount was used until 1987, when Canon introduced the EF lens mount, to be used with the Canon EOS cameras.
The Nikon F, releasedin March 1959, became enormously successful, and became the camera that demonstrated Japanese camera manufacturer’s superiority. The F featured Nikon’s 3-lug bayonet F mount, still used today with slight modifications to keep with the times. The F also featured many other elements that added up to its success:
1- An interchangeable prism and focusing screen system.
2- Mirror lockup, which reduced vibration, by making the mirror flip out of the light’s path just before the shutter opened.
3- A solid design, making it resistant to damage.
4- 100% viewfinder
5- It was released with a wide variety of lenses, ranging from 21mm to 1000 mm focal length.
Minolta released the SR-2 to global market the same the Canonflex and the F, although the SR-2 had been on sale in Japan since 1958. The SR-2 featured Minolta’s MD mount (still used today) along with a semi-automatic diaphragm.