... for a cave survey then, if you were to reproduce that as an A2 poster, 600 dpi would be acceptable because its twice as big and you would stand twice as far back to view it. An A0 poster might get away with 300 dpi lines. ...
I think that generations of cavers who have stood in the long common room at Penwyllt and squinted at the detail of the OFD survey, which is in effect somewhat larger than A0, will disagree with you on viewing distances, Dave.
