4.5mm f/2.8 EX DC HSM for Sony
Circular fisheye lens for APS-C DSLRs.
One of the most unusual lenses in a photographer's kit, the circular fisheye produces a round image with a 180 degree field of view in the center of the frame. This makes the lens useful for creating extremely exaggerated images, panoramas, and, thanks to its equisolid angle projection, it is also useful for scientific applications. To combat flare and ghosting Sigma employed Super Multi Layer lens coatings, and Special Low Dispersion glass elements reduce chromatic aberration.