photo:sigma20mm
Sigma 20mm f/1.4 DG HSM Art full frame lens
introduction
20mm super wide angle full frame lens in various mounts
world's first ƒ/1.4 ultra wide angle lens for full frame dSLRs (Nikon has a 20mm ƒ/1.8G lens, Sigma had a cheaper 20mm f/1.8 EX and then there is the Leica 21mm f/1.4, a $6,700 lens for rangefinders)
no filter thread!
not weathersealed!
specs
20mm super wide angle full frame lens
no filter thread!
not weathersealed but will take a light shower
Sigma uses a new material called TSC (Thermally Stable Composite)
HSM AF
close focus 0.276m giving 0.14x macro
15 elements in 11 groups, and includes 2 FLD (“F” Low Dispersion), 2 SLD (Special Low Dispersion) and 2 Aspherical elements
9 rounded blades
90.7mm x 129.8mm
950g
$US900
reviews
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3.4EV vignetting, reducing to 1.85EV at f/2 and 1EV at f/2.8
2.44% barrel distortion
very soft corners wide open, corners and centre sharpest at f/4
1px CA - well controlled
far better bokeh than most wide angle lenses
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coma is an issue though until you stop down to f/2.8
there is some sort of weird field curvature or other blooming effect happening at f/1.4, through the whole image
awesome sunstars but the rounded blades mean points are not as sharp
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mild coma and astigmatism - acceptable for stars / Milky Way astroscapes
sharper than the Nikon and Canon 24mm f/1.4 lenses in the center, and at least equal in corner resolution
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for
astrophotographic landscapes of the Milky Way, the Rokinon/Samyang/Bower 24mm f/1.4 manual focus lens has slightly better star shapes if you get a good copy, similar vignetting but less build quality, more copy variation, and less sharp in the centre, and of course, is not as wide angle and doesn't have AF or aperture control by camera.
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photo/sigma20mm.txt · Last modified: 2017/03/31 19:43 by gary1