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Title: too soft wide open; inconsistent autofocus
Review: While this lens will allow you to shoot in very low light, the resulting images will be very soft. It sharpens up nicely by f/4, but there are several zoom lenses (e.g. 24-105mm f/4L) that can match it at that aperture. While quick, the auto focus is not very accurate. I spent a lot of time dialing in the AF micro-adjustment on my camera (7D), and while I was able to improve the average case, the variance was just too large to yield an acceptable "keeper" rate.
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