It looked like Nippon Kogaku would be the last company to develop SLR cameras. However, its ideas and designs were ahead of the competition, a reflection of how serious and earnest the company was about SLR technology.
When Nikon's first camera appeared, many professional photographers entrusted it for their most important photos.
Again, when talking about the history of Nikon, it is important to note that the development of the Nikon F was directly affected by the input and influence of professional photographers.
For example, in Japan(Nippon) only Nikon cameras offered interchangeable lenses in the true sense of the word. For domestic cameras compatible with interchangeable lenses, there were in reality only normal lenses available. Problems that would probably occur when using wide-angle or telephoto lenses did not affect those cameras.
For the Nikon S or S2, conversely, 2.8cm and 10.5cm lenses were available in addition to 3.5cm lenses. This reflects the fact that accurate composition and focusing were very important for Nikon cameras and the people who designed them and would use them.
Nippon Kogaku lavished its power and energy on developing the Nikon SP to create an extremely elaborate and super-high-grade camera with built-in viewfinders with a range of 2.8cm to 13.5cm. No camera at that time - not even the Leica M - had this feature.
Nippon Kogaku did its best to develop other features and functions within the limits of building a compact, albeit elaborate, camera. However, the Nikon SP still required an accessory viewfinder for focal lengths not covered by the built-in viewfinder.
In addition, a safety rate was required for frame coverage of the finder. Unnecessary images were always exposed because the actual exposed image area was wider than the area seen through the finder.
Close-up shots were, of course, rather inaccurate, despite that they required very complicated operations.
Nikon users rated the S2 and SP very highly. Ironically, Nippon Kogaku engineers and designers were discontented with the S2 and SP, causing their desire for a more complete camera to grow.