Juste pour info, j'ai trouvé cela sur dpreview :

CANON, publishing the trouble "of EF 70-300mm F4-5.6 IS USM"

CANON on the 24th, recognized the phenomenon where in interchangeable lens "EF 70-300mm F4-5.6 IS USM" resolution becomes insufficient. The schedule which announces corresponding method in late June.

When it photographs at vertical position in near focal length 300mm, those where "there are times when resolution is not sufficient at portion around the photographing picture". Indication from the user was received, you say that phenomenon was verified.

The telephoto zoom lens to which EF 70-300mm F4-5.6 IS USM corresponds to also 35mm format, loads the hand blurring revision mechanism. The design which corresponds to digital single-lens reflex is administered e.g., reflected light from the image pickup element is considered.

Vous en avez déjà parlé sur le forum de ce problème, dans des situations de pdv en verticale, vers les 300mm ?? Si oui, un correctif est en cours...