Can you justify $550 for .4 difference?

[Fotografer]

Looking at the Canon 85 1.8 vs Sigma 85 1.4.</p>
<p>Reading the Sigma review, it's an excellent lens. Seen some shots from a wedding and amazing clarity. But would you spend the $550 for the difference? </p>
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<p><a href="http://www.dpreview.com/news/1002/10022015sigma85mm.asp" target="_blank">Sigma releases 85mm F1.4 EX DG HSM: Digital Photography Review</a></p>
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