The Dallmeyer 3B is a soft focus portrait lens from the long-established London optical maker J.H. Dallmeyer, designed for studio portraiture on large format plate cameras. Often referred to simply as the "Dallmeyer 3B," it belongs to the classic Petzval-derived portrait family used by professional portraitists from the late 19th century into the 20th, prized for its rendering of skin tones and out-of-focus areas rather than clinical sharpness.

UK auction evidence for the 3B Soft Focus Portrait is thin, with a single tracked hammer result of £1,140 in October 2019 — a wholesale saleroom level, not a retail asking price. On that limited basis the lens sells for around four figures at auction today, though condition, completeness of the diffusion control, mount and any matching flange will materially affect what a clean example is worth. Buyers researching what a Dallmeyer 3B is worth should treat this single data point as indicative rather than a firm market price.