08-25-2016, 06:35 PM
(This post was last modified: 08-25-2016, 06:43 PM by Brightcolours.)
It has to do with the optical design, that no UD is used. The design choices, probably with price.
Sigma does use "UD" glass in their lens:
It does not "magically" make corners great:
Sigma does use "UD" glass in their lens:
It does not "magically" make corners great: