Today Pentax announced the smc D FA 645 25mm f4 AL SDM AW lens for the 645D digital medium-format SLR camera. This is the second lens in the 645D series, along with the smc D FA 645 55mm f2.8 AL SDM AW lens($1,100). The new D FA 645 25mm f4 is an ultra-wide-angle lens offering the equivalent focal length of 19.5mm in 35mm format terms. When mounted on a 645 film camera the new lens has an equivalent of 15.5mm. This is the widest of all Pentax 645 lenses.
The 25mm 645D lens, along with the first 645D lens, is part of the All Weather (AW) series, and features a dustproof, weather-resistant construction, an aluminum lens barrel, with 11 seals to prevent dust and water from entering the lens.
To reduce flare and glare, the lens has Pentax's Aero Bright coating; the lens also incorporates two aspherical optical lens elements for maintaining brightness in the corners. There is a supersonic direct-drive motor (SDM) for quiet auto-focus. It has Pentax's Quick-Shift Focus system for on-the-fly switching to manual focus.
Included with the lens is a circular polarizing filter (40.5mm), and the lens has a built-in filter holder, in the barrel, that pulls out; the circular polarizer can be rotated as needed.
The Pentax smc D FA 645 25mm f4 AL SDM AW lens will be available in April 2011 with a price of $4,999.95.