Canon RF-S 3.9mm F/3.5 STM Dual Fisheye Lens

The Canon RF‑S 3.9mm f/3.5 STM Dual Fisheye Lens is a specialized stereoscopic fisheye lens developed for Canon’s RF‑mount mirrorless cameras, targeted primarily at immersive, 3D VR180 video and VR content creation. Unlike conventional lenses that capture a single image, this lens features two synchronized fisheye optical systems positioned side by side, allowing it to capture left and right views simultaneously. This dual‑lens design is ideal for producing true 3D stereoscopic footage — where depth perception and spatial realism can be experienced when viewed in VR headsets or compatible platforms.

Optically, each fisheye system has an extremely wide 144° diagonal field of view, capturing a broad perspective so users can immerse viewers in vivid environments. Each optical path comprises 11 elements in 8 groups with two Ultra‑Low Dispersion (UD) glass elements per lens and Air Sphere Coating (ASC), which helps reduce flare, ghosting, and reflections typical of ultra‑wide optics. The 144° view and optical design balance wide coverage with good overall image clarity, even in tough lighting conditions.

Autofocus on this lens is powered by a gear‑type Stepping Motor (STM) mechanism that moves both lenses in unison. This enables fast, smooth, and relatively quiet autofocus for a fisheye system — a first for Canon dual‑fisheye lenses — with One Shot AF available for ease of use in still and video shooting. For video, autofocus works best before recording; Servo AF during video capture is not supported. Canon also provides focus differential adjustment controls, allowing users to fine‑tune the focus balance between the left and right lenses for optimized stereo capture.

The lens’s f/3.5 maximum aperture provides bright performance for 3D capture, while the minimum aperture of f/16 helps maintain deep depth of field — beneficial for virtual reality footage where much of the scene should remain in focus. The minimum focusing distance is approximately 0.2 m (7.9 in), producing a maximum magnification of about 0.03×, which is suitable for immersive scenes rather than close‑up macro work.

Designed for compactness and portability, the RF‑S 3.9mm Dual Fisheye weighs about 289 g (10.2 oz) with dimensions of approximately 112 × 54.6 mm (diameter × length). Its rear filter system provides flexibility, allowing both 30.5 mm screw‑on filters and gelatin filters to be used — useful for exposure control in bright environments or special creative effects.

Unlike standard lenses, this Dual Fisheye does not include optical image stabilization, as the stereoscopic capture and extremely wide field of view make traditional stabilization less practical. It also lacks dust and moisture resistance compared to more conventional L‑series optics, so users should take care in harsh environments.

The RF‑S 3.9mm f/3.5 Dual Fisheye is particularly compelling for VR content creators, social media storytellers, and filmmakers looking to step into 3D and immersive video without the complexity and cost of multi‑camera rigs. To convert the dual fisheye footage into usable equirectangular formats for editing and playback, Canon provides software tools like EOS VR Utility and plugins for editing applications, enabling workflows for platforms including VR headsets and online 180° video.