From the product specifications, the Irix 11mm f4 lens is a rectilinear ultra wide angle lens with a 126° angle of view, having optical composition of 16 elements in 10 groups, using 4 high refractive lenses, 2 extra low dispersion (ED) lenses, and 3 aspherical lenses. Irix claims the wide angle barrel distortion is well controlled at only 3.13% distortion despite the 11mm ultra wide coverage. The minimum focusing distance is at a respectable 0.275 m (0.9 ft) for an ultra wide angle lens. The Firefly version of 11mm f4 features lightweight construction (which is about 12% lighter than the Blackstone counterpart) and an anti-slip, rubber coated focus ring. The Blackstone 11mm f4 lens is constructed with an aluminum magnesium alloy chassis and has engraved fluorescent lens markings that boost visibility in extremely low light conditions. The Blackstone version has full weather sealing, while the Firefly version has partial weather sealing (the front element of the lens is not sealed).
The ultra wide perspective and added unique features of the Irix 11mm f4 lens made it suitable for outdoor landscape shooting. Having a lens with rugged construction and weather sealing helps when shooting in harsh weather conditions. The Blackstone version of the 11mm f4 lens has UV reflective, engraved markings which aid visibility of the lens markings in near dark conditions: suitable for shooting night scenery and even astro-photography. Furthermore, the infinity position is clearly labeled, and the focusing ring has a noticeable click which makes the manual focus for landscape shooting easy to operate even in the dark.