Digital BW, The Print

on 4/4/02 10:27 AM, John Brownlow wrote:

<Snip>
 
> (5a)    D2 = (Dmax - Dmin') - MAX ( delta (Dn, Dn+1))
> 
> This seems like an achievable measurement and definitely different from the
> original D1 in equation (1). I wonder what, if anything, it really tells us?

John,

I followed along as best I could, but I did get lost (not understanding
delta and all), but here's the deal. By the time you've measured all your
256 density patches, what do you want to do with that data? Do you want to
compress it all into a value like 2.6, or 25db, that really tells you very
little about the characteristics of your print (short of suggesting a
density range), or would you rather plot it as a curve (which is how I've
always seen silver papers characteristics represented), to get a more
meaningful representation of the qualities of said print?

Even with scanners, where Austin's DyR formula is totally applicable, what
does the net result really tell you? The density range the scanner is
capable of before noise becomes intrusive. In electronics we can't see the
noise from outside of the box; on a print, if the noise is the tooth of the
paper, do you really want that characteristic expressed as a number?

Plus much of this discussion so far has focused on the ability of a paper to
separate the first perceptible highlight from dMin. What does it say about a
paper like Somerset Enhanced, which has soft smooth midtones, which some
might crave, in spite of what may be high "noise" and relatively weak
highlight separation? Could you appreciate that characteristic from a single
number?

Ironically, a paper like Torchon, which has a lot of surface modulation,
yields one of the sharpest looking prints out there, at least for larger
prints. And the tooth of that paper seems to be relatively more of a problem
to our visual perception than I'm guessing one would expect from measured
values. So some people hate it for small prints with close viewing
distances, but love it for larger prints with far viewing distances. What do
we do with that?

Todd