Are "bad copies of lenses" really acceptable in 2021?

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mbike999
mbike999 Senior Member • Posts: 1,119
Are "bad copies of lenses" really acceptable in 2021?
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Up front disclaimer - I am by no means an expert on this but just curious about this topic.

I was recently reading some reviews of various lenses and I have also read lens testing and comparison work by folks like Roger Cicala. I have often run across discussions where people say things like "they must have a bad copy" or "I must have got a good copy". My question is thus: if people like Roger can test lenses and detect defects or deficiencies from a spread of identical lenses, then why don't the manufacturers do the same thing? Is it a cost savings thing?

Assuming manufacturers do this level of QA/QC, how do these lenses even pass QA/QC process? With current testing equipment, is it reasonable that a dud lens make it off the assembly line? I would assume there are testing tolerances established that would rule out these "bad copy" issues, but it seems that is not necessarily the case because I still seem to hear about it all the time. Or maybe the manufacturer's tolerances are much more liberal than we might expect?

I haven't personally ran into an issue recently where a lens was badly de-centered, for example, although I have had faulty OIS systems and one lens which was badly blurred throughout the focus range. Of course I'll never know how my lenses compare to other identical lenses.

I find it curious that photographers need to worry about the possibility of getting bad copies when investing so much in glass, especially when there is precise testing equipment available. I know I can't ignore the possibility that damage occurred after international shipping, but I'm just curious about other's thoughts on the issue and what the primary culprit is and whether it is acceptable that lenses can differ in optical output, sometimes widely. This seems especially problematic when practically no one has the ability to test a large sample set of lenses.

I think it would be nice to get a test card along with each lens purchase so that the buyer knows their lens passed with flying colors, and if anything is markedly off from that something disastrous likely occurred in shipping.

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