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Re: [OM] 50mm Lens Versions

Subject: Re: [OM] 50mm Lens Versions
From: "John A. Lind" <jlind@xxxxxxxxxxx>
Date: Mon, 08 Jan 2001 00:42:28 +0000
At 03:23 1/8/01, C.H. Ling wrote:

The SC 5xx I have is an exceptional one, which is the best 50/1.4 (in
resolution) I have ever seen.

One point I'm not quite sure, seems that starting from 5xx,xxx the
construction of 50/1.4 was not changed (except coating), the different
in performance might be came from the manufacturing, as the production
quantity of 50/1.4 was very high, tooling or fixture might wear and
changed a few times during the whole manufacturing history.

C.H.Ling

I will second C.H. Ling's observation about manufacturing variation and tooling wear. I know it all too well with what I do professionally in electronics manufacturing.

I will add that performance variation can also occur in used lenses with their varying condition and generally unknown provenance. A lens may have been damaged and repaired to excellent cosmetics but not to original optical specifications. It is a risk the buyer of any used lens takes, unless the complete provenance of the lens is known, which is quite rare. Additional variation among a range of user observations about performance can also be caused by the fact they are used on different camera bodies. There _will_ be some variation in focusing accuracy (flange to film plane distance versus flange to mirror to focus screen distance) which _will_ confound lens performance. What makes Gary Reese's data valuable is generally consistent use of the same set of camera bodies in his testing . . . which is why I'm glad he has posted which body was used for each test.

While my 50/1.4 MC with 789,### S/N is second to my 50/1.2, it is a very close second, and both are much better than the old 50/1.8 F.Zuiko I bought in 1980. I'm not that surprised that C.H. Ling has a 500,### S/N that performs better than all the other 50/1.4's he has. All the other sources for possible variation in performance can dominate theoretical differences inherent in the designs when you compare specific lenses.

The evidence shows some measurable probability if a specific 50/1.4 "Zuiko" has a S/N >1,100,###, it will be a better lens than a specific "MC" with a S/N <1,000,###, or a specific "G.Zuiko" but it is definitely _not_ a 100% guarantee that it will be. I believe this is all one can legitimately conclude from Gary Reese's testing: statistical significance between the mean performance of entire populations of different versions of the 50/1.4 Zuiko.

-- John


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