Analysis of information sources in references of the Wikipedia article "Zeiss Sonnar" in English language version.
With the emergence of the single-lens reflex camera, the rivalry between the Sonnar-type lens and the [double] Gauss-type lens was finally resolved. As an asymmetrical optical system, the Sonnar-type lens simply could not ensure the back focus necessary for the operation of a quick-return mirror, and thus had to cede the mantle of standard large-diameter lens to the Gauss-type lens. Thus, as the single-lens reflex camera grew in popularity, the Gauss-type lens became the standard large-diameter lens, while the Sonnar-type lens found its niche as a large-diameter telephoto lens, a role for which its short overall length proved advantageous.
The only lenses that could be diverted as-is to use for F-mount cameras were those with a focal length greater than that of the 13.5cm f/3.5. [...] Back focus on the 8.5cm was lacking remarkably, so designers gave up on any thoughts of diversion to the F mount. However, if 10.5cm f/2.5 back focus could be increased by 1-1.5mm, it could be converted to the F mount. By reducing the thickness of the last lens element by 1.0mm, Wakimoto was able to preserve back focus and release the 10.5cm f/2.5 for F-mount cameras.
