Like its predecessor, the f/2.8 Mk I lens was often considered to have excellent contrast, color rendition and decent sharpness wide open. However, some samples of this lens have also been reported to exhibit deficiencies and operational problems not present in the older 28–70mm lens, including poor sharpness and/or chromatic aberration. According to the head of a US lens rental firm, the f/2.8 Mk I lens "definitely has some reliability issues and a lot of copy-to-copy variation, at least some of which relate to its design."