I bought this lens a year ago and took 1000 photos with it. For the price you expect great focus and you get that along with beautiful bokeh. It's light enough to hold in hand with practice. It doesn't have IS and I didn't find it a problem, just use a good shutter speed. I like 1/800 for small birds. Why not buy a Canon 100-400 and take advantage of the zoom range? I read some reviews and spoke to Flickr friends who bought a Canon EF 100-400mm f/4.5-5.6L IS USM and it's not that sharp. A Flickr friend bought this lens and just couldn't get a sharp enough photo to use it. He even sent it to Canon for repairs and he says it's still unusable. I have 400mm f5.6L for the long end. I have other shorter range photography lenses that are smaller and easier to use. At F5.6 the lens is quite slow and needs a lot of light. But to get a faster lens you need about $10,000, and you can't handle a much heavier lens. 400mm 5.6L weighs 2.8lbs. The more expensive version, which is faster, weighs 8.49 pounds. On the field, weight matters a lot. At 2.8 pounds and relatively light, it's still a lot to carry, but it's something you can do. The F5.6L is not a zoom, so there will be no problem if dust gets inside.
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