I take your points Rufus, My comment arises from my experience with
prints - and scanning them at very high resolution to identify tiny details
in the background - often freight cars in a yard of interest. I have found
that a 30 or 50 year old black and white print will provide a lot more
information when blown up that way than will the typical 8x10 print I buy
from the local archives. I suspect that is simply because they scan at 300
dpi, and it isn't sufficient for those tiny details....

Rob Kirkham