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Re: [OM] Radioactive glass

Subject: Re: [OM] Radioactive glass
From: "John A. Lind" <jlind@xxxxxxxxxxxx>
Date: Sun, 27 Jul 2003 20:56:32 -0500
At 12:32 PM 7/27/03, tOM wrote:
Was there ever an M 50/1.2?

No. The 50/1.2 was introduced very late in the OM system (1984 ??), was multi-coated from the outset and has never had the "MC" marking as it was created after the "MC" markings were dropped (1981 ??).

Its predecessor was the the 55/1.2 and I don't know if its lineage extends into the original M-1 from 1972, but it goes back at least to 1974 when the OM-1 "MD" was introduced. At that time (1974) the three "standard" lenses were a 50/1.8, 50/1.4 and the aforementioned 55/1.2, all of which were single-coated. There are supposedly two versions of the 55/1.2, neither of which was multi-coated. The earlier version has a reputation for yellowing, and IIRC two [??] of its glass elements contain slightly radioactive rare earth elements in their glass formulation.

Don't ask me about the 55/1.2 serial number break between versions because I don't know.

-- John

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