This Pentax HD DA 645 28-45mm f/4.5 ED AW SR Lens  is an ultra-wide-angle zoom lens (incorporating the Pentax-original built-in SR (Shake Reduction mechanism) is designed to optimise the optical performance of the new 645Z, and all Pentax medium-format digital SLR cameras. Providing focal lengths from 22mm to 35.5mm in 35mm format, this is the first lens designed specifically for digital imaging. Thanks to its dustproof, weather-resistant construction, this newest member of the AW (All Weather) series offers outstanding reliability and durability in demanding shooting conditions, allowing photographers to capture images outdoors without worry! For photographers looking to produce exaggerated perspective and expanded depth-of-field shots (unique to wide-angle lenses), this lens is ideal for capturing a range of scenes and subjects; from sweeping landscapes to small indoor spaces. If that wasn’t enough… its optics consist of 17 elements in 12 groups, including two high-performance aspherical elements and two ED (Extra-low Dispersion) elements, to enhance image resolution and brightness at edges, while minimizing aberrations. Coupled with a high-grade, multi-layer HD Coating** to optimise light transmittance and minimize reflection, and the Pentax-exclusive, high-grade Aero Bright Coating’ this lens is designed to bring out optimum performance in medium-format digital SLR cameras. * HD stands for High Definition ** A Pentax-original lens coating process developed through the use of nanotechnology. Using a silica aerogel with a uniform porous structure as the base material, this coating produces clear, high-quality images by assuring outstanding anti-reflection performance over a broad wavelength range. Other features include: ・SP (Super Protect) Coating applied to the front surface of the lens to repel water and grease ・A rounded diaphragm to produce a smooth, beautiful bokeh (out-of-focus rendition), while minimizing the streaking effect of light ・Smooth, quiet autofocus operation driven by a built-in DC motor ・Quick-Shift Focus system for instant switching to manual-focus operation after the subject is captured in focus by the camera’s AF system ・Various filters such as the C-PL (circular polarizing) filter can be attached to the front of the lens - a unique feature for a wide-angle lens.
The HD Pentax-DA645 28-45mm f/4.5 ED AW SR Lens from Pentax provides users of the 645D or 645Z with a weather-resistant, ultra wide-angle zoom lens with a 35mm equivalent focal length of 22-35.5mm. This lens features the 645AF2 mount for electronic aperture control and autofocus with an internal DC motor. Also, it has a constant maximum aperture of f/4.5 throughout its zoom range and uses extra-low dispersion glass elements to limit the effects of chromatic aberrations and improve sharpness.
The dustproof and weather-resistant 28-45mm lens features a quick-shift focus system that allows users to quickly switch from auto to manual focus as well as shake reduction image stabilization good for up to approximately 3.5 stops. Further improving image quality is the use of HD and Aero Bright coatings that reduce flare and ghosting. A Super Protect coating on the front element is also utilized to ensure the surface is free of dust and marks.
This lens has nine rounded aperture blades that will provide smooth out-of-focus areas. Additionally, the lens has an 82mm front filter thread and comes with both a case and hood.
Aperture range from f/4.5 to f/32
Pentax 645AF2 mount for full electronic aperture control and autofocus with an internal DC motor
Lens construction features 17 elements in 12 groups <
Maximum magnification of 0.21x
All-weather design is both dustproof and water-resistant
Built-in shake reduction technology provides about 3.5 stops of image stabilization
Nine rounded diaphragm blades provide a circular aperture from f/4.5-6.3 at 28mm and from f/4.5-8 at 45mm
Minimum focusing distance of 1.3'