The Pentax SMC DA 645 25mm F4 AL (IF) SDM AW ($4,999.95 direct)( at Amazon) delivers an impressively wide field of view to owners of the Pentax 645D( at Amazon) medium format digital camera. The lens is equivalent to a 19.5mm optic on a full-frame image sensor, and is a top choice for capturing wide landscapes. It's sealed against inclement weather conditions, just like the 645D, so you can get your shot in harsh elements without worry. You'll have to pay dearly to get such a wide field of view on the 645D's big image sensor, and even though the lens is extremely sharp, it's not perfect. This is the second version of the lens released since the launch of Pentax's digital 645 system. The first, which had a D FA designation, had an image circle large enough to allow for use on film bodies. This version is intended for use with the 645D only, a camera that has an image sensor that isn't quite the same size as a 645 film frame. Like many medium format optics, the 25mm is a big, heav...
The ultra-wide field of view produced by the Pentax SMC DA 645 25mm F4 AL (IF) SDM AW is tough to match in digital medium format, but the lens shows some color fringing in field use.
Ultra-wide field of view; Very little distortion; Quite sharp; Drop-in filter mechanism; Weather-sealed
Very expensive; Exhibits chromatic aberration