Not sure if it's been posted before, I did a quick search but could'nt find a mention of it here yet,
http://www.slrgear.com/reviews/showproduct.php/product/1137/cat/15
Sharpness
The Olympus 14-35mm /2 is a very sharp lens indeed. It is so sharp, in fact, that it is hard to decide on the optimum aperture / focal length combination for optimum sharpness. According to our test results, 18mm at /4 seems to yield about as perfect sharpness as can be obtained, but in reality, you'll be very hard-pressed to notice any differences for sharpness at any aperture below /11.
The lens is optimized for the wider end of its aperture spectrum, providing results for sharpness at /2 that consumer lenses would be envious of at /8
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http://www.slrgear.com/reviews/showproduct.php/product/1137/cat/15
Sharpness
The Olympus 14-35mm /2 is a very sharp lens indeed. It is so sharp, in fact, that it is hard to decide on the optimum aperture / focal length combination for optimum sharpness. According to our test results, 18mm at /4 seems to yield about as perfect sharpness as can be obtained, but in reality, you'll be very hard-pressed to notice any differences for sharpness at any aperture below /11.
The lens is optimized for the wider end of its aperture spectrum, providing results for sharpness at /2 that consumer lenses would be envious of at /8
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