Nikon's high-quality wide-standard zoom — the manual-focus Ai-S Zoom-Nikkor 25-50mm f/4, constant aperture.
The Ai-S Zoom-Nikkor 25-50mm f/4 is a wide-to-standard zoom for the Nikon F system, introduced in the early 1980s to the Ai-S standard. It covered a useful wide-angle to normal range at a constant f/4 aperture and earned a reputation for high optical quality that rivalled prime lenses of its era.
This is a manual-focus Nikon F lens with a constant maximum aperture of f/4 across a 25-50mm zoom range, built to the Ai-S standard for full metering-body compatibility. It operates with normal reflex viewing on the F system. Only the verified focal range, aperture and mount are stated; construction details are omitted to avoid error.
This zoom is regarded as one of the better manual Nikon zooms optically, holding good sharpness and contrast across its wide-to-normal range with well-controlled distortion. It suits landscape, travel, architecture and general shooting where a single lens spanning wide to normal is wanted. Its constant f/4 aperture simplifies exposure across the range.
On the used market the 25-50mm f/4 is moderately priced and sought by those wanting a high-quality manual wide-standard zoom. Inspect the elements for haze and fungus, check coatings, confirm the aperture blades are dry, and test the zoom and focus for smooth action without play. It adapts well to mirrorless as a capable, compact manual zoom.