The Dallmeyer 4.25 Inch f/2.9 Pentac is a large-format lens from the British optical maker J.H. Dallmeyer, supplied for press, aerial and technical photography during the mid-twentieth century. The Pentac series was positioned as a fast objective for its focal length, with the 4.25-inch version covering smaller plate and roll-film formats.

Auction-hammer evidence for this lens is thin: a single recorded UK saleroom result from late 2025 sold for £130, which sets the only firm reference point for what a 4.25 Inch f/2.9 Pentac is currently worth. With just one data point, today's market value should be treated as indicative rather than established, and condition of the glass, iris and barrel will swing what any individual example sells for.