Irix 11mm f/4 Blackstone Manual Focus Lens for Pentax K

Landscape and architecture photographers who need an ultra-wide perspective on their Pentax K-mount full-frame camera will appreciate the Irix 11mm f/4 Blackstone. Its 126° diagonal angle of view captures expansive scenes with dramatic depth, while the robust aluminum-magnesium body and weather sealing ensure reliable performance in challenging outdoor conditions.

Key specifications

• Focal length: 11mm
• Maximum aperture: f/4
• Minimum aperture: f/22
• Lens mount: Pentax K
• Format compatibility: Full-frame
• Angle of view: 126° (diagonal)
• Minimum focus distance: 0.27 m
• Optical design: 16 elements in 10 groups
• Diaphragm blades: 9 (rounded)
• Focus type: Manual focus
• Image stabilization: No
• Filter size: Rear gel filter slot (30 x 30 mm)
• Weather sealing: Yes (3 seals)
• Construction material: Aluminum-magnesium alloy
• Front element coating: Neutrino coating
• Focus lock: Yes
• Depth of field scale: Yes
• Hyperfocal scale: Yes
• Electronic aperture control: Yes (via camera for AE mode)
• Focus ring rotation: 180°

Why choose it

The Irix 11mm f/4 Blackstone combines exceptional optical quality with a rugged, weather-sealed design. Its manual focus mechanism provides precise control, and the included focus lock and depth of field scales make zone focusing straightforward. The rear gel filter slot allows creative filtration without bulky front filters, and the Neutrino coating reduces flare and ghosting for clear, contrast-rich images.

Ideal use cases

• Landscape photography in extreme environments
• Architectural interiors and exteriors
• Astrophotography and night sky
• Creative wide-angle portraiture

Good to know

The lens is compatible with Pentax K-mount full-frame cameras and can also be used on APS-C models with an equivalent focal length of approximately 16.5mm. The manual focus design offers a 180° rotation for precise adjustments, and the three weather seals protect against dust and moisture. A rear gel filter slot accepts 30x30mm gel filters for creative effects.