The Irix 11mm F4 is an ultra wide angle prime lens for full frame SLRs and SLMs.
It is coming in two versions: Blackstone and Firefly. Both feature the same optical formula, but the more expensive Blackstone features an aluminum-magnesium alloy construction, metal-grooved focusing ring, and anti-scratch coating. The Firefly trades these things in order to save you weight and cash. It is cheaper and features an anti-slip rubber focusing ring and a lightweight construction that is 12% lighter than its all metal brother.
Both versions are weather sealed against dust and moisture.
The UV light reactive engraved markings on the Blackstone glow in the dark, making this ultra-wide 11mm the better lens for night shooting.