Even so, you need to stop it down to about F8 for optimum image quality with 6x7, so the F4 aperture is rather trivial IMHO. I have the 80/4 APO-Rodagon-N. It's a nice lens.
I know but for focusing you have a bit more light to go on than with a max aperture of 5,6. Thanks for the comment on the APO version..I feel tempted but I was actually looking to sell things this time, not to buy ;-)