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Forums > Back > Sigma's lousy lens and it's ugly diamond-shaped bokeh (50mm f1.4 ART, Canon full frame)
Brightcolours
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07-07-2014, 08:22 AM (This post was last modified: 07-07-2014, 09:25 AM by Brightcolours.)
Quote:Sorry, I'm very late.

 

The diamond shaped reproduction is likely a result of pinched optics, basically a lens being held in place too tight and causing a physical change in the element. 

 

re: "You don't get astigmatism shapes when you are that defocussed"

 

Astigmatism is present at all focus depths, onion ring bokeh is one manifestation of astigmatism.
Onion ring bokeh is just a sign that an aspherical element is not totally smooth... "production" marks.

And pinched optics?? Really? No.

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Sigma's lousy lens and it's ugly diamond-shaped bokeh (50mm f1.4 ART, Canon full frame) - by Brightcolours - 07-07-2014, 08:22 AM

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