Ross Resolux 11cm/ f4 enlarging lens image by () Part of the serial number sequence of lenses made. Note that the source warns that 'anomalies' exist, and suggests that some lenses, either made by Ross from designs of other companies (such as Zeiss and Goerz), or lenses made for Ross by subcontractors, may have their own serial numbers unrelated to these. Serial nº Year 100 1840 3,000 1850 6,500 1860 12,500 1870 20,000 1875 44,430 1880 47,31x 1885-1890 50,000 1890-1895 81,96x 1911 86,000 1918 95,000 1921 100,000 1924 105,000 1925 110,000 1927 115,000 1930 120,000 1931 125,000 1933 140,000 1939 200,000 1947 213,000 1946-7 250,000 1960 Notes • From: Wilkinson, M, and Glanfield, C. A Lens Collector's Vade Mecum, CD-rom Version 3F. Cornwall, UK: David Matthews Associates. Chapter 11, Pages 87-88. Links • A selection of at. Notes and threads on Dagor lenses Saturday, July 19, 2003 The best book on the essentials of photographic lenes I know is long out of print although I believe there may be a new edition of it available. But note in the picture below that the serial number is the same engraved on the barrel and on the cells. So f6,8 or 1:6,8 is the lager aperture for this lens. The following figures, even in this Goerz scale, are very close to the regular series of f stops. The next 3 pictures are from the Photo Club de Paris magazine in 1899. Goerz Dagor 210mm Question Goerz Dagor 210mm Question::: One Thread I recently purchased a Goerz Series III, No 3 210 mm lens in barrell. Serial # 65213. The numbers that are engraved on the side of the barrel seem a little different from any that I have seen. They are: 4.6, 6, 12, 24, 48, 96, 192, 384. Are these actual f stops or a different system? If so, how do I convert? -- Dave Hammaker (), March 04, 2001 Answers The first standardized series of F-numbers listed by Kingslake was: 1.1 1.6 2.2 3.3 4.5 6.3 9 12.5 18 25 36 50 71 100. Your numbers are similar but not exact. There were also two systems of F-numbers based on the relative image illumination--the Uniform System (US) and a set of numbers devised by a Zeiss lens designer (Paul Rudolph). I'm at a loss as to whether these apply! The US system is based on the square of today's f-number divided by 16. (ex: f/4 equals 4x4/16 or US1.) According to Kingslake, Rudolph's numbers are derived from 'the appromimate value of 10,000/N-squared. Thus, f/9 became 128 in this system.' Sounds like fuzzy math! Where does this leave you? You could measure your lens openings and divide by the focal length to see if your numbers correspond. Wide open, your aperture should be about 45mm wide (210/4.6=45.6). You might also try some tests assuming that your apertures are close to modern, standard scales. Your f12 looks alot like f11 and f22 is pretty close to f24--again assuming your scale measures the aperture vs immage illumination. If the iris does not 'click-stop' you might be able to approximate modern f-stops. Rotating the iris between 6 and 12 will most likely give you about f8. Snap on ratcheting nut driver. Regards, Get a Grip & More RETURN POLICY: We offer a 30 day exchange or refund for any items we sell unless the listing specifically states 'as is.' All items must be returned in original condition.
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