Part 12 : "Nikon FG / FG20"

In order to realize a programmed AE, it is innevitable to control the aperture stop of the lens from the camera body and it is the problem how to realize that with many Nikkor lenses accumulated since the old age of the Nikon F.
With the combination of Nikon F2 Photomic S + EE Control Unit DS-11 (photo left) and Nikon F2 Photomic AS + EE Control Unit DS-12, the method of rotating the aperture ring of a lens direct with a servomotor was adopted.

However, this seemed difficult to equip with the FG since it would make the mechanism too elaborate.
After all, almost only method left to control the aperture stop from the body was to move the automatic aperture control coupling lever which was equipped with every lens.

This automatic stop down coupling lever, however, only transmits those two situations to a lens,
1.) when pushed up to the limit position, it fully opens the aperture stop, and,
2.) when pushed down by the power of a spring, it stops down to the aperture value fixed by the aperture ring, but isn't considered about the situation that the movement of the lever is stopped on its way of the stroke.

Therefore, even when this lever is stopped moving at the same position on the way of its stroke, it differs at every lens, to what extent the aperture stop blades are stopped down.
In many cases, at about the position two(2) steps stopped down, the stroke of the coupling lever reaches about the half way, and in the stopped down region (e.g. f/16 or f/22) the movement of the lever becomes very small.
Such being the case, it is difficult to control the aperture by using the stop down coupling lever. Particularly, in the stopped down region, as a very small movement of the lever should be controlled, it would be difficult to insure accuracy.
So Nippon Kogaku started to standardize the movement of coupling lever to prepare beforehand for the days of multi-mode AE to come.
"AI-S Nikkor" lens was it (This naming is used only in Japan (Nippon). By the way, in Japan, among AI Nikkor lenses, "AI-S" type lenses are distinguished from others in that the smallest stop (i.e. the largest numeral) both in the aperture ring and the view finder indication is colored orange).

Yes, Nikon Series E lenses (see photograph) were they, which were put on sale at the same time as the Nikon EM (See part 11.).

As soon as they were announced at the "PMA" convention in the spring of 1979, quick-sighted people noticed the difference between them and the AI lenses and it was talked about here and there : "What is this boss on the protection ring of the rear of the lens ?", "What is this cave in the mount ?"

As Nippon Kogaku K.K. didn't give any particular comments and kept silent, many guesses appeared in articles of camera magazines.

Looking them back now, most guesses were right, but there seemed to be no one who investigated the relation between the aperture stop and the movement of the automatic aperture coupling lever.
Anyway, the preparation for the automatic aperture stop control had already been stepped silently three years before the release of the Nikon FG.

The interesting thing is that the "sash" was revived, which was omitted from the EM.
When I interviewed the designer in charge of the EM, to write the article of the previous part (part 11.), I heard the phrase "EM without a sash" repeatedly.
This "sash" means the black-painted part between the leather trim and the top and the bottom cover.
This part seemed to be a symbol of the high class model from the standpoint of the good looks.
Actually, the painting of this part took much process time and was a cause of lowering the rate of acceptance because it was a subject of the appearance inspection.