An ultra-wide circular fisheye lens for APS-C cameras.
The Sigma 4.5mm f/2.8 EX DC HSM Circular Fisheye is a circular fisheye lens for APS-C DSLRs, producing a full circular fisheye image (180-degree diagonal coverage) with black borders on APS-C sensors. DC indicates APS-C image circle; EX = Sigma professional grade; HSM = Hyper Sonic Motor for quiet AF.
4.5mm focal length, f/2.8 maximum aperture, circular fisheye (full 180-degree circular image on APS-C), DC (APS-C image circle), EX/HSM construction, Canon EF-S mount.
The circular fisheye at 4.5mm produces a fully circular image with dramatic spherical distortion on APS-C sensors. Used in astronomy, scientific imaging, and creative photography. The full circular fisheye can be converted to a dome-projection or equirectangular format for 360-degree applications with appropriate software. HSM enables autofocus.
Test the circular fisheye projection on an APS-C body to confirm full circular image coverage. Inspect elements for haze and coating condition. Test HSM AF function. Confirm Canon EF-S mount engagement. The full circular coverage requires an APS-C body — on full-frame it would only show a portion of the circular image.