I last looked at the Pentax 645Z back in 2014; see my in-depth review of the Pentax 645Z and/or view Pentax 645Z and 645D and Pentax medium format lens coverage.
In field of view and depth of field terms, the Pentax HD 35mm f/3.5 AL [IF] is equivalent to a 27.3mm f/2.8 lens as compared to a full frame DSLR (using the long side of the frame).
At about $1599 the Pentax HD 35/3.5 offers high performance at relatively modest cost. Field shooting suggest that it is significantly better corrected than its 55mm f/2.8 sibling (about $925). In particular, field curvature is well controlled, and with only modest peripheral focus shift.
This aperture series with the new Pentax HD 35mm f/3.5 AL IF yields highly useful insights into the performance of this relatively modestly priced wide angle lens for the Pentax 645Z or Pentax 645D. I think it will go a long way to answering questions about its performance capabilities.
Includes image sizes up to 25 MP in both color and black and white*, along with very large crops, at f/3.5, f/5, f/6.3, f/9, f/11 plus RawDigger exposure info.
* Black and white conversion settings also shown.