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Sigma's lousy lens and it's ugly diamond-shaped bokeh (50mm f1.4 ART, Canon full frame)
#2
Your lens is a bad one. Not just a bit off, a lot off. One to return.

 

I just tried mine on a simulated starfield (painted some white dots on black background on computer screen). Using AF (previously micro-adjusted) I took an in focus shot wide open using it on a 5D2. Dots remained mostly circular, with minor signs of astigmatism in corners.

 

Switching to MF, I focused in front of the monitor plane. The bokehballs remained circular with a slight green fringe. This may be stronger if the contrast was higher. Cats eye effect started to happen away from centre. There was also a horizontal cut in the bokeh on the side closest to the centre, presumably due to the rectangular mirror box in camera. The rear element of the lens is bigger than the short side of the mirror box!

 

I repeated this, now focusing behind the monitor. The bokehballs remained circular with a magenta fringe. There was also the cats eye and chopped effect, but this time on the outside of the balls.

 

I don't know what element(s) need to be out of place to create the diamond effects but that lens is not functioning as designed while it does so.

<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
  


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Sigma's lousy lens and it's ugly diamond-shaped bokeh (50mm f1.4 ART, Canon full frame) - by popo - 07-04-2014, 08:34 PM

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