I through the Pentax 645 FA 80-160mm F4.5 on the Pentax 645z. The lens itself is rather sharp, but its HEAVY when attached to the Pentax 645z. I realized that even at 1/500 of a sec the images can have some camera shake to them as well. The lens has nice contrast and I really enjoyed shooting with it.
Here are some images from today with the lens!