Canon's FD-mount constant f/4 telephoto zoom — classic manual-focus design for FD system.
The Canon FD 70-210mm f/4 is a constant-aperture telephoto zoom for Canon's FD-mount film SLR system. The constant f/4 was a distinguishing feature over variable-aperture consumer zooms of the era.
Optically good for its era — the constant f/4 provides consistent exposure throughout the zoom range. FD mount. Manual focus with smooth helicoid. The 70-210mm covers standard telephoto to portrait range.
Canon FD mount — breech-lock or New FD bayonet depending on version. Constant f/4. Manual focus and aperture. Metal construction. The FD mount does NOT adapt well to Canon EOS without quality-reducing corrective optics.
Available used very cheaply. FD lenses adapt to mirrorless cameras (Sony E, Fuji X, MFT) via simple adapters. The constant f/4 is the main appeal. For FD film system users or mirrorless adapter enthusiasts wanting a constant f/4 manual tele zoom.