This Lens is Soft
Canon Rumors in conjunction with Lens Rentals have written a long article on:
Lens Rental, like their name says, rent lenses for Canon, Nikon… They have a fairly high traffic and a big turnover on both cameras and lens. People rent the lens for the weekend or a few days… and inevitably, people complain that the lens, they just rented, is a dude. Why is it soft?