Originally posted by bossa Are the new 645 SDM lenses fully 645 (non cropped) compatible?
PS: Previous poster answered this question. If true, a strange "oversight" by Pentax as a full sized 645 sensor (56 x 41.5) would be a killer proposition.
Lens names may start with the letters A, FA, D FA and DA.
A is manual focus full 645
FA is autofocus full 645
D FA is digital-optimized full 645
DA is digital 33x44mm
The 55mm, 90mm and 25mm are all D FA, and will cover full 645, but the new DA 25mm with the longer hood will vignette on 645.
The DA 28-45mm is the only lens explicitly designed for the 33x44mm sensor, or so Pentax claims on it's website, but no one is sure at what focal length it would vignette yet - there is a difference between how a lens is supposed to be used and how photographers use them. I refuse to believe that a lens that big doesn't have an image circle that extends well beyond the actual sensor.
There can still be a full size sensor Pentax 645X or whatever it'll be called, but only if and when Sony manufactures such a beast that's suitable for mass production, and the only lens that may suffer for it is the 28-45mm, although it's a pretty amazing piece of glass as it is. Maybe they'll offer a crop mode for shooting with DA lenses, but it would be counter-intuitive to be putting down thousands of bucks for a top-tier wide-angle just to crop.
A larger sensor would be a big boon to photographers using legacy lenses, as they would get more use out of them, but focusing on DA and making sharper and higher quality lenses would be better in the long term, as the lens lineup will eventually get replaced with lenses that are better suited for digital CMOS.