Sinh Nhut Nguyen , February 24, 2009; 11:31 P.M.
My most used lens, light and sharp wide opened, its focus is very fast and accurate. Isn't a very sexy lens due to no image stabilization and f/5.6. Most people will over look this lens and go for the faster* but shorter 300mm f/4L IS or the more versatile 100-400mm f/4.5-5.6L IS, but if you shoot bird at the longest end of your lens and don't have money for the $5800 500mm f/4L IS or the $7800 600mm f/4L IS, nothing beats the price, reach and image quality of this lens. Paired with an 1.6x camera like the 40D it becomes 640mm, a very respectable super telephoto. As long as you have a shutter speed of at least 1/1000 camera shake is neglegible. Built Quality is supert too.
*Keep in mind, when shooting bird that you need some depth of field to keep everything in sharp focus.