Canon FL 35mm f/2.5 was a wide-angle prime for Canon's then-new breech-lock FL-mount SLR system, launched in 1964 alongside bodies such as the Canon FX, predating the later FD lens lineup by several years.
It was built from 7 elements in 5 groups, with a 6-blade diaphragm closing to f/16, a preset ring paired with a separate aperture ring for stop-down metering, a 58mm filter thread, a 0.4 metre minimum focus distance, and a weight of 352 grams.
The FL system's semi-automatic diaphragm feels deliberate next to later fully automatic FD lenses, since the shooter works a preset ring rather than relying on full-aperture metering. Rendering follows 1960s Canon wide-angles: solid centre sharpness wide open, with softer corners easing by f/5.6.
It mounts natively on FL and FD-mount Canon SLRs, so use on EOS or mirrorless bodies needs an adapter and stop-down metering. Buyers should check the preset and aperture rings turn smoothly, confirm the diaphragm blades snap shut cleanly, and inspect the coating for cleaning marks.