"Sharp copy" is the phrase sometimes used by photographers to say that the image quality (sharpness in particular) of this particular version of the lens is good. When something is mass-produced, designs are made which define the ideal size, along with the upper and lower limits for tolerance away from this ideal size, for every piece (every screw, hole, seal, etc.) in the final product. When it comes to making a lens, these variances apply to the glass as well as the metal housing. Sometimes a lens which might pass quality inspection at the factory might perform worse than another lens that came off the same production line at a different time.
by netinept July 30, 2012