I've used this lens heavily over the last year and I'd say its a decent beginner's zoom lens. The lens is pretty lightweight, easy to use, and has a good focal range, but using the longer lengths can be tricky since there isn't image stabilization. You get some slight optical imperfections at 300mm as well and the image quality can be a bit soft at times. If you want a zoom lens for occasional use, this is fine, but people who rely on this focal range, especially professionals, may want to look into the IS version or Canon's 70-200mm f/2.8 IS II lens. if your hobbyist, though, this lens is convenient to have.
The 50mm f/1.4 lens is great for some things. The bokeh is rather nice and, at f/1.4, is easy to produce. The lens focuses quickly and the build quality is decent. However! My particular lens back-focuses terribly. The 7D allows me to compensate for this by adjusting the particular lens' focus profile, but it's still not spot-on. At f/1.4, images are nowhere near sharp. They're usable, at best. Stopped down to f/2, things start to look better, but I don't usually shoot wider than f/2.8 if I want sharpness. Even there, it's a tad soft. Chromatic aberations! Ewww! I see blue, purple, and sometimes red halos and highlights. The lens is great for some things, but not quite what I had hoped.
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