I’ve got scratches on the lens coating of my SC and wonder how it could have caused a blur at the center of my images even though such defect does not affect the images of my other cameras that has similar coating scratches. I’ve concluded now that the lens itself is slightly abraded when the coating was scratched off but this abrasion is not visible to my eyes, only the coating scratches are. The next step now is to figure out how to polish the lens; I think the coating is toast.