B00SLP0VA0 Samyang 12 mm T3.1 Fisheye VDSLR Manual Focus Video Lens for Nikon

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Nano Coating System (NCS) reduces reflections and provides higher contrast
Extra low dispersion (ED) and glass aspherical lens (ASP) elements
De-clicked aperture movement and toothed focus and aperture rings provide smooth operation while shooting video.
Circular aperture with 7 blades