Nikon AF Nikkor series lenses

A line of lenses designed for Nikon 35mm SLR cameras having an autofocus motor. There is no AF-drive motor built into the lens, the lens autofocus system is driven from a motor within the camera body via an AF-coupling. With this type of lens, there can be no autofocus operation unless a digital or film SLR camera with the autofocus motor built-in to the camera body is used. Selected digital SLR cameras such as the D3000 series or D5000 series do not have an autofocus motor built-in to the camera body because most lenses produced for these cameras have one in the lens.

Internally the lenses are fitted with a CPU to communicate specific lens data to the camera's autofocus drive and exposure metering systems, via a set of electrical contact pins located around the rear edge of the lens mount.

Compared to the non-AF Nikkors, the focusing helixes were replaced by a cam construction similar to that employed in zoom lenses to change the focal length. This was done for two reasons. First to reduce the load on the focusing motor, which would otherwise have had to move the traditional greased helixes, and second to increase the response time of moving the lens elements to provide a sufficiently quick AF system.

The very low resistance to the rotation of the focus ring when operating these lenses manually and their narrow focus rings did little to endear them to professionals and enthusiasts alike. Beginning in 1988 Nikon responded to the criticism from photographers concerning the design of the first generation AF Nikkors, and began to replace them with lenses that have more traditional, wider rubber coated focusing ring, and a greater focusing resistance to improve their manual focus action.

A new version of AF lenses was introduced at the same time as the F90. These have a modified CPU that provides the approximate focus distance of the lens to the camera in order this information can be incorporated with the exposure calculations performed by the camera's metering CPU. These AF-D Nikkors are a key component of the 3D Matrix-Metering system. The same technology is also included in the newer G-type lenses.

The G type marks the end of the near universal compatibility of Nikkor lenses with all camera bodies from the Nikon F SLR of 1959 onwards. The reason for this is simple: the G types have no aperture ring. They are intended for cameras that allow the aperture to be set via a control on the camera body.