[davidmanze]

This applies more to young mirrorless players than DSLR users.  Canon and Nikon have... decades of experience building AF and IS lenses and have tight tolerances - according to roger @ LR only 2-3% of lenses from each of them are sent back as duds. 

 

As far as copy-to-copy variance when out of spec lenses are removed, canon varies ~7% and sigma varies over twice as much at ~13%.  They absolutely are not beating canikon at tolerance levels, and Zeiss is even better than those two. 

 

 

 

Maybe it applies more to mirrorless I cannot say, what I can say however it "definitely" applies to DSLR users with regard to Pentax, Sigma, Tamron and some others. From Canon and Nikon I cannot say. My personal experiences from Sigma, Pentax and Tamron are poor,these are in the Pentax mount.

 

 Below par modern lenses purchased: 

Sigma EX 10-20mm 4/5.6 decentered returned repaired, a decent copy.10 week wait.

Sigma 50-150mm EX II F2.8, badly decentered, shop exchanged for a good copy

Sigma  18-50mm EX  F2.8  badly decentered   sold on at a loss.general disgust.

Sigma 50-500mm EX  F4/6.3 bought S/H  decentered at 50mm , living with it as I use the longer end. 

Tamron 17-50mm decentered returned repaired, a good copy. 11 week wait

Pentax, DA 21mm F3.2 Limited, decentered, returned was sent another good copy.

Pentax DA* 16-50mm decentered returned for a refund. 

 Good modern lenses purchased.

Pentax FA 50mm F1.4

Sigma 105mm EX F2.8 Macro

Samyang 8mm Fisheye F3.5

 

 

. I've never had a decentered all metal lens going back to the seventies, I still have a few all are perfect.

 

     Statistics will never be complete and we will only know of a small percentage of lenses sold, that's the reality, in the end I'm only interested in "the lens I have in my hand" not the statistical ones!  I now have all the lenses I need, and am taking a permanent sabbatical from lens buying. 

Let's hope that Sigma's promise of tighter quality control is a reality, so far I've seen very little of decentering in recent reviews of the art and their other series.

BTW.  I hold Roger Cigala of Lens Rentals in very high esteem, he's doing a great job!