Some people praise this lens, others praise it. You've all heard the 50mm 1.8, right? This Sigma lens has almost the same price-to-sharpness ratio. It's not as bright as a 2.8 lens, but it's not as expensive either. If you can afford it buy a 2.8 lens, if not then this is the lens you need. It is very sharp but softens on the outer edges.
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