Pentax has unveiled a new wide-angle lens for the 645D camera. It makes sense to have an extremely high resolution optic with this angle of view, to take advantage of the cameras 40mp sensor.

While it costs, it does seem on paper at least to be a thought out design and feature list.

Here are the official details:

 smc PENTAX-DA645 25mm F4AL [IF] SDM AW

A high-performance, unifocal lens, exclusively designed for the PENTAX 645D to produce breathtaking ultra-wide-angle images.

Image © Pentax/Ricoh Imaging Company

22nd of March 2012, 11:00PM CET
PENTAX RICOH IMAGING COMPANY, LTD. is pleased to announce the launch of the PENTAX-DA645 25mm F4AL [IF] SDM AW.
Designed for exclusive use with the PENTAX 645D, this unifocal, ultra-wide-angle lens features PENTAX-original optics optimised for high-quality digital photography to ensure exceptional high resolution images. The sturdy construction of the lens, which is dustproof and weather-resistant, makes it ideal for outdoors photography.

The smc DA645 25mm f/4 AW will be available from mid-April 2012, at the RRP of £3999.99

Major Features
1. Unifocal, ultra-wide-angle lens
When mounted on the PENTAX 645D medium-format digital SLR camera body, this ultra-wide-angle lens offers a focal length of approximately 19.5mm in the 35mm format, providing the widest perspective of all the lenses compatible with the PENTAX 645D. Creating visual effects unique to ultra-wide-angle lenses, such as exaggerated perspective and extra-wide depth of field, it can be effectively used for a wide range of subjects and situations, including spectacular landscapes and indoor shooting within a confined space. This lens gives the PENTAX 645D greater photographic freedom and flexibility.

2. State-of-the-art optics
Incorporating two high-performance a-spherical optical elements within its optics, this ultra-wide-angle lens provides exceptional image-resolving power with outstanding brightness levels even at the edges, whilst keeping any aberrations to a minimum. All lens characteristics are optimised for digital photography, for instance – exclusive lens coatings are applied to optical elements, while anti-reflection materials are applied to the interior of the lens barrel. The result is a lens that brings out the full potential of the PENTAX 645D medium-format digital SLR camera.
3. Aero Bright Coating to dramatically improve transmittance
This lens is treated with a PENTAX-original Aero Bright Coating, which ensures outstanding anti-reflection performance over a broader wavelength range to deliver images that are brighter and of higher quality. Created using PENTAX’s advanced nanotechnology, this exclusive coating reduces lens reflections and greatly improves light transmittance by forming a silica aerogel layer with uniform pores on the surface of the optical elements.
4. Dependable dustproof, weather-resistant construction
As the newest model of the dependable AW (All Weather) series, the lens comes in a highly dependable dustproof, weather-resistant construction with 11 special seals to effectively prevent the intrusion of dust and water into the lens interior. By coupling this lens with the PENTAX 645D camera body, the user is assured of a durable, reliable digital imaging system that performs superbly in demanding outdoor settings — even in rain and mist, or locations prone to water splashes or spray.
5. Mountable circular polarising filter
The lens features a built-in, pull-out-type filter holder in its barrel. By placing the C-PL (circular polarising) filter (40.5mm in diameter; included as an exclusive accessory) on this holder, the user can easily rotate the filter to obtain the desired polarising effect.
6. Smooth, quiet SDM autofocus operation
The advanced SDM (Supersonic Direct-drive Motor) autofocus mechanism has a supersonic motor installed inside the lens barrel which ensures a smooth, quiet autofocus operation.
7. Other features
・  High-quality machined aluminium parts, including the lens barrel, hood and cap
・  The built-in lens hood is optimally shaped for the angle of view when the lens is mounted on the PENTAX 645D camera body
・  Quick-Shift Focus system for instant switching to manual-focus operation, after the subject is captured in focus by the AF system
・  Rounded diaphragm to produce a smooth, beautiful “bokeh” (out-of-focus rendition), while minimising the streaking effect of point light sources
・  SP (Special Protect) coating applied to the front surface of the lens to effectively repel dust, water and grease

End. (22/03/12).