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10-11-2011, 06:35 PM   #16
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One thing about Sigma's use of APO to describe their lenses: Sigma is rather loose in the term's application. Which means, what THEY call APO ain't necessarily what anyone ELSE calls APO. A true apochromat lens meets certain specs; see the Wikipedia entry. Fairly cheap Sigma zooms don't necessarily focus 3 diverse wavelengths of light to the same point. Tsk tsk...

I've read that the cheap utilitarian Industar-50/3.5 is APO. Sure is sharp anyway!


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