Circular fisheye producing full 180-degree hemisphere on Canon APS-C with HSM autofocus.
The Sigma 4.5mm f/2.8 EX DC HSM Circular Fisheye is a specialist lens for Canon EF-S mount APS-C cameras that produces a full circular fisheye image within the sensor frame. The circular projection creates a complete 180-degree hemisphere captured as a circle surrounded by black borders, useful for scientific, creative, and all-sky applications.
Optical quality is good for a fisheye lens with the EX build tier and multi-coating controlling flare effectively despite the extreme 180-degree field of view. The HSM autofocus motor provides fast, quiet focusing, unusual for a fisheye lens where manual focus is typically sufficient due to the enormous depth of field.
Build quality follows Sigma's EX standard with a robust barrel and the quality expected of their premium line. The bulbous front element is characteristic of circular fisheye designs and prevents the use of front-mounted filters. A petal-shaped hood is built into the lens design to protect the protruding front element.
On the used market, the Sigma 4.5mm circular fisheye is one of very few circular fisheye options available for Canon APS-C. For astrophotographers capturing all-sky images, scientists needing hemispherical documentation, and creative photographers wanting the distinctive circular projection, it provides a unique capability at accessible prices.