Nikon’s Roots Vol. 12 – Nikkormat / Nikomat FTn

The FTn is a Center-weighted Nikomat

The Nikon F Photomic Tn was released in 1967, and the Nikomat FTn was released in October, six months after it. In terms of order, the Nikomat FT was a model that incorporated the center-weighted metering developed for the Photomic Tn, but in fact, it was not just that. It was the first model to incorporate the “clack-clack system” that was adopted in Nikon’s TTL metering SLR cameras for the next 10 years.

What is the gacha-gacha (or clack-clack) system?

Even if you say “the gacha gacha system,” only a very small percentage of Nikon users know what it is (Editor’s note – I guarantee NOBODY outside of Japan will understand it unless you watch anime). As mentioned in the Nikomat FT section, Nikon’s crab-claw aperture linkage is for an external light exposure meter, so it does not contain the lens’ maximum aperture F-number information required for TTL maximum aperture metering. Therefore, every time you change lenses, you have to set the maximum aperture F-number of the attached lens to match the film sensitivity scale. This is not only cumbersome, but also carries the risk of forgetting to set it. So, Nikon came up with the gachapon system in an attempt to somehow improve this maximum aperture F-number setting.

When changing lenses on the Nikomat FTn, which uses this rattle-clack system, the user first turns the aperture ring to the minimum aperture after attaching the lens. This makes a clicking sound and resets the previous settings, and then turns the aperture ring until it hits the limit of the maximum aperture. This operation sets the maximum aperture of the newly attached lens in the camera’s TTL metering system. As the aperture ring makes a rattle sound when turned to this maximum aperture, it came to be called the “clack-clack system.” Note that this is merely a nickname and not an official name recognized by Nikon.

In any case, this function was revolutionary because it allowed long-time Nikon users to use the latest TTL open aperture metering with their existing lenses without the troublesome procedure of having to re-adjust the film sensitivity every time they changed lenses. This gacha-gacha system was then incorporated into all Nikon TTL SLR models, and continued for 10 years until 1977.

The mechanism behind the gachapon system

So, how does this “clack-clack” system work? Basically, the lens’s claws are set at the F5.6 position initially. When you turn the aperture ring from this position to the maximum aperture, the angle of rotation represents the number of stops from F5.6 to the maximum aperture of the lens, so the camera body reads the maximum aperture information from there and uses that to correct the exposure meter’s interlocking mechanism.

The Nikomat FTn has a double aperture linkage ring, one of which is linked to the lens’s claws to transmit the movement of the aperture ring, and the other has a film coated with a variable resistor attached to it. This resistor ring has ratchet teeth, and the claws on the ring linked to the claws fall into these ratchet teeth, causing both rings to rotate together. When the aperture ring is turned to the maximum aperture position with the lens attached, the claws fall into the ratchet teeth at a position corresponding to the angle of rotation, setting the maximum aperture. After being set, the two rings rotate together as described above, and the angle of rotation, which includes the maximum aperture information, is input into the TTL metering circuit as the value of the variable resistor.

During this operation, the claws on the ring that is linked to the crab claws make a sound as they slide over the ratchet teeth on the resistor ring. This sound is why it is called the “clack-clack” method.

Reset Mechanism

With this ratchet mechanism, when a new lens is attached, the maximum aperture of the previously attached lens must be reset. This is equivalent to removing the pawl that had fallen into the ratchet teeth from the teeth. In the case of the Nikomat FTn, the mechanism for this is actually built into the back of the nameplate on the front of the pentaprism. There is a gap at the bottom of the nameplate, from which a lever peeks out. One end of the ratchet pawl protrudes from the pin that connects to the crab claw of the aperture interlocking ring, and when the aperture ring is rotated to the minimum aperture after the lens is attached, this touches the lever protruding from the nameplate, resetting the ratchet pawl. After resetting, the lever on the nameplate side retracts, and does not appear until the next time the lens is removed; it is a clever mechanism.

Appearance differences

The Nikomat FTn is a minor change to the FT, so they look very similar in appearance, but it is surprisingly easy to tell them apart. The most noticeable difference is the thickness of the nameplate. The Nikomat FT had a simple plate, but the FTn has a rattle-type reset mechanism built into it, which makes the nameplate thicker. Also, the shape of the attachment part for the pin that works with the crab-shaped claws of the aperture interlocking ring has changed, but this is to hide the reset mechanism. Also, the lens maximum aperture scale on the film sensitivity setting section has been removed, so the area around the shutter dial on the lens mount has been made neater.

The Nikon F Nikomat FTn gained popularity as the younger brother model of the Nikon F, and was a long-selling model that continued to sell for nearly eight years until 1975. During that time, various small improvements were made, but the most noticeable of these was the addition of plastic finger rests to the film advance lever and self-timer lever. This was a small improvement made in response to the release of the Nikon F2 in 1971, and plastic finger rests were also added to the Nikon F.

One thing that is surprisingly little known is the release screw. The Nikon F and F2 did not have the typical tapered screw, but rather a cap screw like the Barnack Leica, in other words, a type of screw cut around the shutter button. The Nikomat FT and FS used the typical tapered screw, but midway through the Nikomat FTn, a cap screw was added around the shutter button, allowing both types of cable release to be used. This was carried over to subsequent Nikomat models, and continued up to the Nikon FM and FE.