Here is a summary or excerpt from an article that has just been published on DPNow:

Developed as the first model of the PENTAX-D FA 645 lens series, it not only features new optics optimized for high-quality digital photography to assure exceptional image-description performance, but also provides an image circle covering the image area of existing 645-format film SLR cameras.
Click here to read the whole article...

Developed as the first model of the PENTAX-D FA 645 lens series, it not only features new optics optimized for high-quality digital photography to assure exceptional image-description performance, but also provides an image circle covering the image area of existing 645-format film SLR cameras.
Click here to read the whole article...