It's rare to find really wide angle full-frame still lenses even remotely this fast, so the fact that Sigma has gotten this to an f/1.4 (and under $1,000) is pretty amazing. Most 20mm lenses are around an f/2 or f/2.8, with Nikon making a particularly speedy 20mm f/1.8. There isn't a giant difference between f/1.4 and f/1.8, but the fact that all of the prime lenses in the Art series have consistent f1/.4 apertures is fantastic, and this one should fit nicely with the 24mm f/1.4, 35mm f/1.4, and 50mm f/1.4 lenses already in the series. This 20mm will come in Canon EF, Nikon F, and Sigma SA mounts.
Here are the specs:
- Comes in Canon EF, Nikon F, Sigma SA Mounts
- Covers Full-Frame 35mm
- Aperture Range: f/1.4 to f/16
- Two FLD Elements and Five SLD Elements
- Two Aspherical Elements
- Super Multi-Layer Coating
- Hyper Sonic AF Motor, Manual Override
- Rounded 9-Blade Diaphragm
- TSC Material, Brass Bayonet Mount
- Minimum Focus Distance: 10.9" (27.69 cm)
- Built-In Petal-Shaped Lens Hood
- Compatible with Sigma USB Dock
- Dimensions (DxL): Approx. 3.57 x 5.11" (90.7 x 129.8 mm)
- Weight: 2.09 lb (950 g)
- Availability: November 2015
- Price: $900
While there are faster and wider lenses out there, they are mainly PL cinema lenses that only cover Super 35mm and cost more than your car. If this 20mm is anything like the others in the Art series (which we expect it will be), it's going to be on the sharper side. The only question will be distortion. Once you get this wide, keeping straight lines straight starts to become rather difficult, and that will likely be more of a deciding factor than speed at this wide of a focal length.
If Sigma completes the long end of this Art line, it would be interesting to see a cinema version with gears and smooth iris. At the moment there is really nothing that competes with the price/feature set of the Samyang/Rokinon cinema series, so hopefully other manufacturers will catch on and produce lenses that have all of the features filmmakers want, but won't completely break the bank — and deliver stellar image quality.