A Deep-Dive Into Nikon’s Legendary 105mm f/2.5 Lens

Produced in various configurations over the course of 50 years, Nikon’s 105mm f/2.5 lens is considered by many to be one of the best optics the company ever made. In his latest Dino Bytes video, Gordon Laing takes a look at the history and image quality of this much beloved lens.

Originally released in 1954, the Nikkor 105mm f/2.5 underwent multiple iterations through its half-century life. The one Laing owns is a K-version, one of almost 58,000 units produced between 1974 and 1977 and a glance at the serial number puts his somewhere closer to the beginning of that run. The optics of the lens were changed a couple of times, and Laing’s unit features a design that was updated in 1971.

Before that, the lens featured Sonnar type optics in a construction of five lenses arranged into three groups. As explained in a detailed breakdown on Nikon’s Thousand and One Nights blog, one of those groups appears particularly thick when looking at charts of the arrangement beecause it includes three lenses that were fused together, which Nikon explains created sharp, “solid” images.

As both Laing and Nikon explain, the lens underwent a major design change in 1971 and was released in a lens that would be known as the Nikkor Auto 105mm f/2.5. The design for this lens continued for three generations, from the Nikkor Auto, to the new AI Nikkor, and then to the AI-S Nikkor.

“And surprisingly enough, the AI Nikkor 105mm f/2.5S… still uses the same basic design: a design on the market for 34 years,” Nikon’s Haruo Sato writes. “The superior performance of this lens is proved by the fact that the basic design required no changes over 34 years.”

The biggest changes to the lens over that time were, therefore, its external design as well as how the lens communicated with various Nikon cameras.

“For the models produced up to 1977, including my own sample, the aperture was communicated using a coupling affectionately known as rabbit ears, which mated with a pin on the camera body. These are known as non-AI or pre-AI lenses,” Laing explains. “Then Nikon came up with a new means of communicating the aperture to the body known as ‘auto indexing’ or AI for short. These feature a ridge or tab on the back of their aperture rings that pushes a lever around the mount on newer bodies, but for backwards compatibility with older bodies, the rabbit ears remained for some time.”

The AI-S 105mm f/2.5 had the longest production run of all the 105mm iterations, from 1981 through 2005.

The 105mm f/2.5 remains one of the most popular compact telephoto lenses Nikon ever produced due to its sharpness as well as the lovely rendition of defocused areas. It actually became the perfect example of how good bokeh could be on a Nikkor lens, as prior to its release there was a stigma that while Nikkor lenses were sharp, the defocused area was less appealing.

The venerable lens was discontinued in 2006.

Image credits: Nikon, A Thousand and One Nights