retrofocus lens

optics

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Last updated

July 13, 2026

Quick Summary

A retrofocus lens is a type of wide-angle lens used in cameras, particularly single-lens reflex (SLR) cameras. SLRs require a specific distance between the lens and the film to accommodate a swinging mirror. Retrofocus designs achieve this by making the back focus—the distance from the rear glass surface of the lens to the focal plane when focused on a distant object—longer than the lens's focal length. This design allows for wide-angle capabilities while maintaining the necessary clearance for the camera's mirror mechanism, ensuring optimal image performance.12

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technology of photography
Wide-angle and retrofocus lenses
Short-focus, wide-angle lenses are usually mounted near the film. Single-lens reflex cameras need a certain minimum lens-to-film distance to accommodate the swinging mirror. Wide-angle (and sometimes normal-focus) lenses for such cameras therefore use retrofocus designs. In these the back focus is appreciably longer…
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Short-focus, wide-angle lenses are usually mounted near the film. Single-lens reflex cameras need a certain minimum lens-to-film distance to accommodate the swinging mirror. Wide-angle (and sometimes normal-focus) lenses for such cameras therefore use retrofocus designs. In these the back focus is appreciably longer…
Read More