Lens quality control

Started Sep 24, 2013 | Discussions thread
ProfHankD
Senior MemberPosts: 2,161Gear list
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Sample variation is not that big a deal
In reply to nevada5, Sep 25, 2013

From what I've seen, sample variation is larger on newer autofocus lenses than on old manual lenses. This makes sense in that motor drive for focus, etc., requires less friction and somewhat looser fits. The older lenses also tend to have fewer and all spherical elements, which also help.

However, I think a lot of what's going on also has to do with the modern practice of designing tooling to "wear through" a tolerance range. The machinery may be capable of tighter tolerances than things made years ago, but this ability is used to control placement of values so that they vary within the allowable tolerance range for the longest possible time without needing frequent (or 100%) testing/readjustment to confirm things are still in tolerance.

In any case, relax. As usual, LensRentals is right that the out-of-spec lenses stand out against the normal variation, and normal variations often trade one aspect for another rather than being one good vs. one bad.  Don't use the out-of-spec lenses and things will be fine. The reason there are design tolerances is because the designer and manufacturer analysis said that within that range things work well enough... which they generally do.

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