I was given a box of old lenses by a friend, and came across only one that's different. It's a Vivitar 135mm f/2.8 auto lens. I'm not familiar with the lens mount. After comparing both Nikon dimensions on Wikipedia and some information and images on the Pentax K-mount, I've drawn a blank as to which of these it could be. Now the "NI" in red on the lens flange, could it be a Nikon mount? My measurements with my caliper didn't agree with picture of the dimensions on Wikipedia.

lens top view of flange lens side view of flange lens side view

  • \$\begingroup\$ That is certainly not PK but might be the old Nikon mount, as they had an external catch for the aperture selection as seen on yours, IIRC. You can see examples on the WP page, under "Nikkor": en.m.wikipedia.org/wiki/Nikon_F-mount \$\endgroup\$ May 16, 2022 at 23:07

1 Answer 1


Vivitar rebranded lenses made by other manufacturers. Your lens is made by Tokina with a T4 or TX universal mount, which uses adapters to fit different cameras. The TX mount is a revision of the T4 mount to add features needed by some newer camera systems. The universal mount can be identified by the locking ring marked "O ←⋅→ L".

If you are using a film camera, you may be able to find a compatible T4/TX adapter. Although the two are not entirely compatible, some TX adapters are just relabeled T4 adapters, and some T4 adapters are listed for sale as TX adapters.

Attached to the universal mount, you have an adapter for the pre-AI version of the Nikon F mount. The most prominent feature of this mount are the "rabbit ears" without holes. There is no AI coupling (ridged aperture ring), AI-S notch, or electronic contacts, which are seen in later revisions of the mount.

From the position of the stop pin under one of the tabs, you can see that the lens turns counter-clockwise to lock. Nikon F and Nikon Z are the only mounts I have encountered that lock in this direction.

If you plan to use the lens with a digital camera, I recommend stacking another adapter on top of the existing Nikon F adapter to fit your camera. Nikon F has a long FFD that is easy to adapt to many other camera systems.

annotated image

  • \$\begingroup\$ Fabulous, thanks for this! For the record I have now verified that this is a T4 lens mount after removing the adapter, which means that other adapters can be swapped in - to a degree as I understand. \$\endgroup\$
    – Fowler440
    May 17, 2022 at 12:11
  • \$\begingroup\$ There are T4 adapters for other mounts. Sometimes they are listed as TX, but the two are not always compatible. (Some TX adapters are just relabeled T4 adapters.) If you are using a digital camera, I'd recommend keeping the existing Nikon F adapter and stacking another adapter to fit the camera. \$\endgroup\$
    – xiota
    May 17, 2022 at 14:40

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