I Have A Bad Copy Of Lens X

When reading about different lenses or browsing through used lens ads (don't all photographers do that??) it is hard not to read that this is 'a great copy' or a 'soft copy' of any given lens.  We all want those great copies......right?  Well here is a great article about why that great copy of a given lens might not be so great on your particular camera body........that, and lots of other interesting information about why manufacturing tolerances guarantee differences between samples of any lens on today's high resolution digital cameras. This is a really interesting read.  Check out "This Lens Is Soft And Other Facts" here.