Sigma Photo 20mm f/1.8 EX DG ASP RF

Light-gathering wide-angle lens for full-frame and APS-C cameras (Canon mount)

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Item #: 366411CA

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Get the big picture — indoors

Say you're at the society event of the season, and you've been asked to document the event. The locale? A large, high-ceilinged hotel ballroom downtown, complete with a stage that houses a 19-piece big band. Oh, yeah, it's also pretty dark. How do you show people the scope of the place? How do you show people having fun without putting a flash unit in their faces?

Time to consider one of the most light-sensitive wide-angle lenses available today: the Sigma Photo 20mm f/1.8 lens. With its wide aperture that's perfect for low-lit interiors, you'll be snapping away in seconds, and, if you're shooting on a full-frame camera, everyone will get an idea of the grandeur and scale of what's going on. Even on an APS-C camera, you'll have a wide-angle 30-32mm focal length. Plus, the lens is perfect for landscapes and architectural photography as well, as you'll be able to fit a lot into one frame. Features like aspherical lens technology and a rear focusing system ensure that your images will have minimal color fringing and deliver solid image quality across the entire frame.

Product Highlights:

  • Canon EF-mount
  • 20mm f/1.8 EX DG ASP RF wide-angle lens with 35mm equivalent of 32mm on Canon cameras with APS-C sensors
  • Super Multi-Layer Coating minimizes reflections and flare
  • light-gathering wide field of view is ideal for landscapes, exterior and interior architecture, and photojournalism
  • minimum focusing distance: 7.9"
  • constructed of 13 elements in 11 groups
  • filter size: 82mm
  • lens is 3.5" in diameter, 3-3/4" long
  • weight: 18.3 oz.
  • carrying case, lens hood, front and rear lens caps supplied
  • warranty: 4 years
  • Our 60-day money-back guarantee

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Hands-on research

What's in the box?

Download owner's manual

  • Sigma 20mm f/1.8 EX DG ASP RF lens for Canon
  • LCF-82 II lens cap (installed)
  • Rear lens cap (installed)
  • LH875-02 Lens hood
  • Soft padded case
  • Instructions
  • Warranty Card
  • Limited Warranty sheet

Features and Specs

Brand Compatibility Canon
Image Stabilization No
Focal Length 20mm
Maximum Aperture f/1.8
Weight 18.3 ounces
Parts Warranty 4 Years
Labor Warranty 4 Years

Product Research


Overview: The Sigma 20mm F1.8 EX DG Aspherical RF is a fast, ultra wide angle lens, designed to be used with full-frame cameras. It is a great lens for taking portraits, as well as for travel, weddings, and other events. The lens has the Canon EF-mount.

Lens Hood: The Sigma 20mm lens includes a lens hood to help prevent stray light from entering the lens, causing flare, and to protect the lens from rain, snow, and dust. When not in use, the lens hood can be inverted and mounted onto the lens backwards for storage.

Focus Mode Switch: The lens features a two-way switch for setting the focus mode: AF (auto focus) or MF (manual focus).

Sigma Technology: The lens has the following Sigma technology built-in:

  • Aspherical Lens: Aspherical lenses are used for outstanding optical performance and to keep the lenses compact.
  • Super Multi-layer Coating: Sigma's own Super Multi-layer Coating suppresses lens flare and ghosting by preventing reflections within the lens.
  • Rounded Diaphragm: Using a rounded diaphragm instead of a polygonal shaped one produces pleasingly rounded out-of-focus light points when opened to near maximum aperture.
  • Rear Focusing System: Sigma uses a focusing system that moves the rear lens group, for high speed, silent focusing.


  • Lens Construction: 13 Elements in 11 Groups
  • Angle of View: 94.5°
  • Number of Diaphragm Blades: 9
  • Maximum Aperture: f/1.8
  • Minimum Aperture: f/22
  • Minimum Focusing Distance: 7.9"
  • Filter Size: 82mm
  • Maximum Magnifications: 1:4
  • Dimensions: Diameter=3.442", Length=3.731"
  • Weight: 18.3 ounces

Our Product Research Team

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