Versatile Ultra-Wide Prime. With a focal length equivalent to 31.5mm after crop-factor and a 92° angle of view, the Pentax HD PENTAX-D FA 21mm f/2.4ED Limited DC WR is an exceptional choice for architectural photography, landscape photography, and all-around interior and exterior shooting. Its constant f/2.4 aperture lets you work in low light and gives you great depth-of-field control for selective focusing.

High-Quality Optical Design. The eight-group/eleven-element optical design features four Extra-Low Dispersion elements and one Super Extra-Low Dispersion element to help minimize chromatic aberrations and color bleeding while maximizing clarity and sharpness. Pentax’s HD coatings reduce reflections and lens flare, and Super Protect coatings on the front and rear elements repel dust, water, and oils.

Electromagnetic Diaphragm. The ED in the 21mm f/2.4ED’s name refers to its large electromagnetic diaphragm mechanism, which is designed to deliver precise exposure control when used with a compatible DSLR. It helps ensure smooth video capture even in locations with rapidly changing lighting or brightness conditions.

Supersonic Direct-Drive Autofocus and Quick-Shift Focus. The direct-drive motor offers fast, nearly silent autofocus performance with an internal-focusing design. The Quick-Shift Focus System gives you full-time manual focusing for quick adjustment, and a focus-range limiter improves focus performance when strictly shooting subjects at a great distance.