Nikon AF-S 20mm f/1.8G ED £650/$800
Surprisingly small and light for a 20mm lens
The two Nikon lenses on test are the lightest of the bunch, at 355g each. This lens is about the same size as the Samyang 20mm, but feels a little less robust, although it adds a rubber weather-seal ring on the mounting plate. The Nikon also adds ring-type ultrasonic autofocus, whereas the Samyang is manual focus only. The Nikon is therefore a better option if you prefer to rely on autofocus.
However, despite the focus distance scales, the rotational travel of both Nikon lenses is small, making accurate manual focusing tricky. Like the Nikon 24mm lens, it features two ED and two aspherical elements, and Nano Crystal Coating.
At f/1.8, vignetting is the worst of any lens in the group, and corner sharpness is quite disappointing. However, you only need to stop down to f/2.8 to get decent peripheral illumination, while f/4 improves sharpness across the frame. The Sigma 20mm lens offers better image quality and a faster aperture, but the Nikon lens is much more compact.