Irix 15 mm f/2.4 Blackstone
7. Coma, astigmatism and bokeh
| Center, f/2.5 | Corner APS-C, f/2.5 | Corner FF, f/2.5 |
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| Center, f/3.5 | Corner APS-C, f/3.5 | Corner FF, f/3.5 |
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Night sky shows a similar situation. Once again on edges of full frame you can notice distinct deformation of images of stars and they are shaped exactly like the diode presented earlier.
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| Canon 5D Mk III, JPEG, f/2.5, upper right corner of the frame 1:1 |
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The astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to just 3.1% so shouldn’t be very bothersome. The official result of the Samyang 2.8/14 was even lower but both these values are alike within the margin of error and both remain practically imperceptible.
The blurry out-of-focus areas are quite nice for a lens with such parameters. Defocused circles of light don’t have any worrying features: the light spread is even, without any distinct rims or local extremes.
| Center, f/2.5 | Corner APS-C, f/2.5 | Corner FF, f/2.5 |
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| Center, f/3.5 | Corner APS-C, f/3.5 | Corner FF, f/3.5 |
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Center, f/5.0 | Corner APS-C, f/5.0 | Corner FF, f/5.0 |
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