A medium format autofocus telephoto lens for the Mamiya 645AF and Phase One systems, noted as the longest in the 645 lineup at its release.
Overview
This is the Mamiya 300mm f/4.5 AF APO, a long telephoto lens designed for medium format photography using the 6x4.5cm frame. Built for the Mamiya 645AF and Phase One camera systems, it features apochromatic correction and autofocus operation driven by the camera body. At the time of its release, it was the longest lens available in the Mamiya 645 lineup.
Specifications
| Focal length | 300mm |
| Maximum aperture | f/4.5 |
| Minimum aperture | f/32 |
| Apochromatic correction | yes |
| Autofocus | yes |
| Lens mount | Mamiya 645AF and Phase One |
| Filter size | 77mm |
| Angle of view | 14° |
| Maximum format | Medium format 6x4.5 |
Design
The lens features an apochromatic (APO) optical design to minimize chromatic aberration and deliver high sharpness and clarity. Autofocus is driven by the camera body motor, and moving parts inside the lens barrel should not be touched during operation, per Mamiya's safety guidance.
Context
Positioned as the longest lens in the Mamiya 645 system at its release, the 300mm f/4.5 AF APO filled the telephoto niche for medium format photographers needing reach without sacrificing optical quality. It was not rebadged or offered under the Phase One brand at the time of its introduction, remaining a Mamiya-designed optic for both compatible systems.
Reception
Described as a high-quality medium format lens capable of exceptional clarity and sharpness, it demands precise technique. Users note that achieving sharp results requires a stable tripod, a high-quality head, and careful handling—especially given the challenges of long focal length on medium format film or digital backs.
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