Irix's budget ultra-wide prime — 15mm f/2.4 with weather sealing in the lighter Firefly build.
The Irix Firefly 15mm f/2.4 is an ultra-wide prime from Irix's Firefly series — the more affordable, polycarbonate-housing tier versus the premium all-metal Blackstone. Designed for landscape, astrophotography, and architectural photography on full-frame cameras. Manual focus with hard-stop infinity focus. Nikon F mount.
f/2.4 maximum aperture. 15mm focal length. Manual focus only. Hard-stop infinity focus (mechanical stop at infinity for accurate night-sky focusing without guessing). Polycarbonate housing (Firefly tier). Full-frame coverage. Nikon F mount. At approximately 430g.
The hard-stop infinity focus is a deliberate design for astrophotography: the focus ring has a physical stop at the infinity position, enabling reliable infinity focus without live-view magnification in the dark. The Firefly polycarbonate housing provides lower weight and cost than the Blackstone metal version, with the same optical formula. The 15mm f/2.4 provides adequate aperture for Milky Way photography without excessive coma wide open.
On the used market the Irix Firefly 15mm f/2.4 Nikon F is an affordable manual-focus ultra-wide for landscape and astrophotography. Condition checks: polycarbonate housing for cracks or mounting stress marks, hard-stop infinity focus engagement, front element for marks, aperture blade smoothness. Manual focus only. The Blackstone version offers the same optics in an all-metal housing.