SMC Pentax Bellows 100mm f/4

Notes and sources

Minimum aperture confirmed in the original Asahi Pentax Lenses brochure, lens specification table (PDF page 11). The manufacturer leaves minimum focus blank because this is a bellows lens: the bellows extension determines focusing range. No fixed standalone minimum distance is invented. The brochure lists 186g versus the existing specialist figure 185g; existing weight is retained rather than treating a 1g source discrepancy as a distinct generation.