Irix 15mm f/2.4 Firefly £425, $480 www.irixlens.com
Irix is a notable newcomer in the world of ultra-wide primes, blending Swiss design with Korean manufacture. The 15mm Firefly lacks autofocus, but will communicate with your Nikon in the standard PASM shooting modes. It features two aspherical, two extra-low dispersion and two high refractive index elements, which deliver terrific results, although we experienced a few exposure inaccuracies with our test sample. At f/8 the Firefly matches Nikon’s 14-24mm f/2.8G, while producing noticeably less fringing and half the barrel distortion. Excellent ergonomics round off an impressive package.