This SLR TTL-AE system took a long time to develop, and it was not until 1969 that the first prototype of Nikomat EL was actually made.
The electronic version of the Copal Square S shutter unit used for the Nikomat FT had been already developed, which was called the Copal Square SE.
This was adopted into the shutter mechanism of this first prototype, which was called "5B", as a member of the Nikomat lineup (Photo: Left).
This initial prototype was designed to look like a compact
version of the Nikomat FTN (1967) (See Part 6.).
The heart of the camera's electronic circuitry was made of several transistors situated in the "control section" under the shutter dial.
This is a hub of the camera, in a sense, because a galvanometer to indicate the automatically controlled shutter speed and a pointer to indicate manual set shutter speed were also installed in this section.
The 5B prototype was successfull, but a major problem arose just before moving to mass production.
This camera's shutter control circuit used a system known as "logarithmic compression/expansion method", which might have impinged upon another company's patent.
Countermeasure had to be urgently taken and thus several ideas were considered.
The problem was finally resolved by adopting the more practical,
"bi-logarithmic compression" system.