Dilemma of the electric switch
With the "Nikomat EL", the film-advance lever (stand-by position : 30 degrees) is used to switch the power ON and OFF, more commonly known as "film-advance lever switch".
Since the shutter of Nikomat FTN and Nikon F2 is mechanically controlled, the switch does not have to be turned ON at the time of shutter release.
However, with the electronically controlled Nikomat EL, the shutter speed is not controlled if the power is ON, thus when the power switch is OFF, the shutter button is designed to be locked.
In this connection, if there is no battery, the only mechanically controlled shutter speed, 1 / 90 sec., works.
The film-advance lever switch is effective with preventing to forget to turn the power OFF. It is because you can recognize either the power is ON or OFF, since it is near the position of the film-advance lever, which is a rather big parts of the camera (also, when putting the camera in the hard case and covering the front cover, you can prevent from forgetting to turn the switch OFF).
If it is a TTL-SLR camera that uses CdS for the photocell, you can put a cap on the lens (and the eyepiece) so that the light does not hit the photocell. By doing this the electric consumption will be less than micro-ampere, so you don't need to worry about turning the switch OFF.
However, with an electronically-controlled camera like the Nikomat EL that has a complicated electronic circuit, the story is different. Regardless of the intensity of the light which hits the photocell there is a constant flow of electricity by the order of milli-ampere (mA), so if with a small battery, it will die out in a few days.
Thus, with the Nikomat EL, the film-advance lever switch was important. It's a whole new story with Nikomat ELW or Nikon EL2, which can attach the autowinder. If film-advance is done by the winder, then there is no need of a lever. It is inconvenient to pull out the film-advance lever, which sticks out from the camera back, just to turn the power ON.
So, with the two models that can attach the autowinder, there is a small lever around the shutter button area, and this lever, the "shutter button switch" also functions as power ON / OFF switch and shutter button lock (See photo).
In order to use the autowinder, the "film-advance lever switch" is moved back flush to the camera body, and this "shutter button switch" becomes the ON / OFF switch.
Although this does not come in the way of film-advancing, a problem of forgetting to turn the power OFF has increased.
- Shutter button switch
(The small lever around the shutter release button area : Photo of EL2)
There was a big dilemma where by making the power switch parts conspicuous it will reduce the chance of forgetting to turn the power OFF, but it becomes inconvenient when shooting.
If it is inconspicuous, then there will be more chance of forgetting to turn the power OFF.
This was a problem which continued until the "time switch", which goes off after a certain time lapse, was adopted to cameras like Nikon EM (1980) and Nikon F3 (1980).