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 p.4 #9 · *Samples* Zuiko MC 24-40mm f4 | |
Congratulations on a great find. Many things have already been said, and to have the accompanying US patent is certainly helpful to evaluate the history of that lens.
It was mentioned that the lens does not have the white 4-digit code at the back of the lens: that is no surprise, as this 4-digit code was only used since spring 1983. Before that, on many -but not all- lenses, a production code can be found below the rubber of the focusing (or in this case, might be zoom) ring. Up to the end of 1977, a three-digit code was used: first letter a katakana character, where I, Sa and Shi indicate production at the Olympus plants Ina, Sakaki, and Shirakawa, respectively. Second digit corresponds to the last digit of the production year (e.g., "6" = 1976), the third digit/letter is the production month (1 ... 9 Jan to Sept, X, Y, Z, for Oct to Dec). From ca. 1978 to spring 1983, the katagana character was replaced with a roman letter (A, E, G, K, L, P and W are known) probably also indicating the manufacturing plant. The front ring reading "ZUIKO MC" also indicates production before the end of 1981, when this was changed to "ZUIKO" only for all lenses, though old front ring were used up for some time, which in your case is irrelevant, as it is a prototype.
I am guessing that the patent filing date 02-23-78 will be close to the production time of your lens. A number of US patents for the OM Zuiko lenses have been filed just a few months before mass production incl. export to the US have started. These US patent seem to follow sometimes after a number of japanese patents have already been filed.
It was mentioned that some elements appear yellowish. I am also guessing that these are due to single layer amber coating, and are unrelated to "rare earth" glasses. Olympus had quite some problems with multicoating of photographic lenses up to the mids of the 1980th, and many of the "Multicoated" lenses have only a few elements actually with MC, whereas others were only SC. Yellowing of glass elements in old lenses can be due to the use of radioactive rare earth glasses, mainly Thorium, which allowed to increase the Abbe numbers (= low dispersion). You can easily check with a Geiger counter whether there is any detectable radioactivity. I certainly doubt this, as the main glass producers have stopped the manufacturing of such radioactive glasses by the mids of the 1970th. In thee case of the 55/1.2 OM ZUIKO lens, Olympus changed the original Thorium containing glass around 1977 to non-radioactive glass. If you don't have a Geiger counter, probably the physics teacher of your local High School has access to one, or any Physics, Biochemistry or Cell/Molecular Biology Department at the University will have one (it's a 10s job to check).
The tables for the four different "Embodiments" in the patent indicate that there is not any need for exotic glasses: the refractive indices and Abbe numbers are all quite in the usual range (I have checked the 1981 Schott optical glass catalogue, so it is not that I'm talking about newer glass mixtures). Your color scheme of the lens cross section refers only to embodiment 1; however, the patent is for four different constructions. I think that the 3rd and 4th cross section can be excluded, as there focal range would be limited to 24-35mm, but the 2nd cross section might be also a possibility: the main difference is that the 2nd and 3rd elements are cemented together is example 1, whereas they are separated in example 2 (i.e. 11 elements in 9 groups construction). When you see "haze" at the 2nd element, and it is indeed the construction corresponding to embodiment 1, there is a good chance that it is lens separation. Olympus had such problems with the contemporary 75-150/4 and 85-250/5 zooms as listed in their repair manuals.
Here my guessing on why Olympus has decided against mass production of this lens: the specs were probably not good enough. When compared to the 28-48mm f/4 S-Zuiko lens released in early 1982, it is 35% heavier, 22% longer and, despite that at that time it would have been the wide angle zoom with the smallest filter size (others were 58 to 77mm), the final lens could be reduced to a 49mm filter size. Then there comes the economics: the final 8 elements in 8 groups design was much cheaper to construct than an 11/8 or 11/9 design, especially with respect to the cementing of groups.
History has shown that Olympus (it's a company to make profit, and not a charity to produce outstanding lenses) made the right decision: your 24-40/4 lens would have probably cost about as much (or more) as the 35-70/3.6 lens, whereas the 28-48/4 was considerably less expensive, and still sold only 20,000 samples. If people wanted a lens like yours, they could get several 3rd party alternatives as mentioned in previous posts.
Have you tried to get information on the history of your lens from the previous owner? Was he, or the owner before, affiliated with Olympus? It seems that Olympus has given out prototypes for field testing to various people sympathetic to them; Franz Pangerl (author of "The World of the OM System") seems to have received such a 100006 or similar sample of the 35/2.8 shift lens, which was also in development for a couple of years.
Edited on Apr 04, 2008 at 02:09 PM
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