Quote Originally Posted by Shaggy
if a lens covers a 20" horizontal dimension. why wouldn't it cover a 14" vertical?
because what is important is the diagonal coverage. If the diameter of the circle is 20 inches, then half of that would be 10 inches and it wont cover. It is simple geometry. If you make sure the lens convers the diagonal then it will cover both the horizontal and vertical dimensions.

The Nikkor 450 wont cover 14x20, it covers 12x20 with about an inch an a half of movement up or down, 2 inches and you start seeing vignette, I have plenty of negs that have this.

IMO I would rather mask the vignete than show a print with vignetted corners, I think that is sloppy printing, but to each its own.