Rokinon RK20M-P 20mm f/1.8 Wide Angle Lens Pentax

The Rokinon 20mm f/1.8 ED AS UMC is a manual-focus wide-angle prime lens built for Pentax K-mount DSLRs. Its optical formula consists of 13 elements arranged in 12 groups, incorporating 2 aspherical elements to control distortion and field curvature, along with 3 extra-low dispersion elements that minimize chromatic aberration. The result is a lens that delivers sharp, detailed images across the frame, particularly useful for landscape, architectural, and astrophotography where edge-to-edge clarity matters. The Ultra Multi Coating helps maintain contrast and color accuracy even when shooting toward light sources.

At f/1.8, this lens gathers a significant amount of light for a 20mm optic, making it well suited for night sky photography and dimly lit interiors. The relatively close minimum focusing distance of 0.66 feet adds creative flexibility for environmental portraits or detail shots with a wide perspective. While the manual-focus-only design requires more deliberate shooting, many photographers find this an acceptable trade-off for the optical quality and price point. The included lens hood, caps, and pouch round out a package that is ready to use straight from the box.