Bests & Worsts Reviews from Amazon

Reviews of this lens on the web are mixed with some showing soft results, particularly at 400mm. This is likely due to wide variations in sample lenses. I decided to take a chance and seem to have gotten lucky. My copy, just received from Amazon (Build date of Oct 2005) produces fantastically crisp and contrasty images on my 20D at ALL focal lengths from 100 to 400. It's almost magical. The images are much sharper using the same f-stops than those from a 70-200 f2.8IS lens at 100-150mm and virtually the same at 200mm. Even wide-open at 400mm this lens is quite sharp. At 400mm, I've compared to a very nice Canon 400mm f5.6L prime lens, with and without 1.4X teleconverter. The images have virtually the same extreme sharpness and contrast if the zoom is stopped down just one one-third stop (e.g. zoom at 6.3, prime at 5.6). With the 1.4X TC both lenses had to be manually focused but produced outstanding clarity with NO perceivable loss in quality. The focus is swift and true and the IS on this lens really works (and does not hum like that on the 70-200 f2.8IS) allowing handheld shots at 1/100 sec at 400mm. It may be that Canon has quietly improved this lens since recent reviews seem to be much more positive than those from a few years ago. Some folks don't like the push-pull zoom but it works great for me and allows very fast composition of scenes. The lens is about the same size as the 70-200 f2.8 IS but seems lighter and better balanced. Given the razor sharpness of its images and 100-400mm range, this seems like the perfect single lens solution for nature and bird photography. However, it is big and white so it may not be the best for candid people photography.