Bonjour,

Tout d'abord voici un lien :

http://www.photozone.de/lens-test-faq

Va faire un tour sur ce site, tu pourras te faire un comparatif des 2 zooms à ouverture identique. Tu verras que le f4 IS, hormis qu'il n'ouvre pas à 2,8 obtient des résultats bien meilleurs que le f2,8 IS.

Je ne trouve pas cela spécialement logique parce plus tu prends un zoom de grande ouverture, plus tu payes, plus tu es en droit d'exiger de la qualité mais de part ce qui est incrit les f2,8 IS ne sont pas sans problèmes : Voici quelques extraits

Problème de différence de qualité entre 2 zooms différents :

"Two sample of this lens has been tested. The first sample performed quite poor and the 2nd sample did outperform its quality figures but not without problems. This 2nd sample has been tested once more after a calibration by the Canon service."

Conclusion :

"The Canon EF 70-200mm f/2.8 USM IS is a very good lens but not a stellar one. The resolution characteristic is excellent at 70mm and 135mm but at 200mm it disappoints - more so regarding its price tag. The results are still very good here (just at f/2.8) but when putting things into perspective (e.g. vs the superb EF 70-200mm f/4 USM L IS) the delivered quality is not overly impressive. Based on the performance at 200mm the potential with tele converters seems "limited". Lateral chromatic aberrations (CAs) are relatively well controlled but, again, inferior to the in-house competition (inc. its predecessor). Distortions are nothing to worry about as is vignetting. The build quality of the lens is superb and the IS as well as the very fast AF makes it a joy to use. If only it was better at 200mm ... "

Vis à vis de tout ce qui précède, je pencherais plutôt pour le f4 IS.

Salutations

Emmanuel