{"overview":"The Dallmeyer 51mm f\/1 Oscilac 4:1 is a specialist ultra-fast lens from the long-established London optical maker J.H. Dallmeyer. With a maximum aperture of f\/1 and a stated 4:1 reproduction ratio, it was built for oscilloscope-trace recording and similar scientific imaging tasks rather than general photography.","market_narrative":"At recent UK auction, hammer prices for this Oscilac have ranged from £250 to £650, with the two recorded results in 2023 giving a midpoint near £450 — wholesale saleroom levels achieved before buyer's premium. Specialist scientific optics like this attract a narrow pool of bidders, so today in 2026 what one sells for can swing widely depending on cosmetic condition and whether the original mounting hardware is present.","buying_guide":"Inspect the front and rear elements carefully for fungus, haze and cleaning marks, since the large air-spaced groups of an f\/1 design are particularly unforgiving of internal contamination. Check for any signs of separation in cemented groups, oil migration on the iris if fitted, and confirm the barrel threads and flange are intact, as these industrial lenses are often missing the adapters needed to mount them.","specs":"The lens is a 51mm f\/1 objective designed for a 4:1 reproduction ratio; no further manufacturer specifications are provided in the source data.","faq":[{"q":"What is a Dallmeyer 51mm f\/1 Oscilac 4:1 worth today?","a":"Based on UK auction hammer results, value has ranged from £250 to £650, so a fair price guide for a clean example sits around the middle of that band."},{"q":"How much does a Dallmeyer Oscilac sell for at auction?","a":"The two recorded 2023 UK sales hammered at £250 and £650, reflecting the narrow but variable specialist market for ultra-fast oscillograph optics."},{"q":"Was the Oscilac designed for normal photography?","a":"No — the 4:1 designation and f\/1 aperture indicate it was built for oscilloscope-trace recording, and adapting it to a stills camera typically requires custom mounting."}],"confidence":40,"reasoning":"Only two sales records and no SPECS or variant data are provided, so confidence is capped below 50 per the rules."}