The Asahi Pentax Takumar 100mm f/4 Bellows is a short telephoto lens designed without a focusing helicoid, intended for use on a bellows unit for close-up and macro photography on M42-screw-mount Pentax bodies. It dates from the classic Takumar era and was aimed at users needing high reproduction ratios where the bellows itself provides focus travel.

UK auction data for this lens is thin: the only logged hammer result is £69 from March 2022, a wholesale saleroom figure rather than a retail or dealer price. On that single data point the 100mm f/4 Bellows Takumar appears to be an inexpensive specialist optic in today's market, and as of 2026 buyers should expect what it sells for to track closely with general condition rather than commanding any clear variant premium.