{"overview":"The Dallmeyer 20 Inch f\/5.6 Telephoto is a long-focus telephoto lens from the British optical maker J.H. Dallmeyer, designed for large-format plate cameras where a narrow angle of view and substantial reach were required. Lenses of this length and aperture were typically used for portraiture at distance, naturalist photography and reportage on plate cameras during the late brass-and-bellows era.","market_narrative":"Auction evidence for this exact reference is thin: a single UK saleroom result from September 2024 saw one sell for £50 at hammer, which is the wholesale level fetched at auction before buyer's premium and excludes seller's commission. With only one data point on file in 2026, that figure should be read as indicative rather than a reliable guide to what a clean example is worth today, and condition, completeness of the iris and the presence of the original flange will move the price materially.","buying_guide":"Inspect the cells under a torch for internal haze, fungus filaments and balsam separation at the cemented interfaces, all of which are common in Dallmeyer telephotos of this age. Check that the brass barrel has not been over-polished, that the iris blades open and close cleanly without oil bleed, and that the focusing helicoid or rack-and-pinion (where fitted) moves smoothly along its full travel; coating scratches are not relevant on uncoated lenses of this period, but front and rear element polish marks are.","specs":"The lens is a 20 inch (approximately 508mm) telephoto with a maximum aperture of f\/5.6, branded under J.H. Dallmeyer; further construction and serial-range data are not on file.","faq":[{"q":"How much does a Dallmeyer 20 Inch f\/5.6 Telephoto sell for?","a":"The only UK auction record on file is £50 hammer from September 2024, so a clean, working example is currently worth around that level at saleroom level, though a single sale is not a robust guide to price."},{"q":"What is a Dallmeyer 20 Inch f\/5.6 Telephoto worth in 2026?","a":"On the available evidence the value sits in the region of £50 at UK auction hammer, but condition of the glass, iris and barrel can push a good copy meaningfully above that figure."},{"q":"Is the Dallmeyer 20 Inch f\/5.6 Telephoto usable on modern cameras?","a":"It was built for large-format plate cameras and has no native modern mount, so use today requires a bellows or large-format setup; adaptation to smaller digital formats is possible but mechanically involved."}],"confidence":30,"reasoning":"Only one sale record and no SPECS or variants are provided, so pricing and technical claims are necessarily limited."}