In my *considerable* experience (thousands of prints since 1974 that led to
4 books plus the acquisition of the Fresson process) with pigment prints
the answer is not that easy. For starter, I won't even touch the definition
of "luminosity".
I have made carbon prints where the pigment would easily rub off on one's
fingers when touched, while others looked like perfect facsimiles of Agfa
Portriga papers. I have often taken pleasure in showing a wide variety of
prints to visitors, asking them how many different processes they could
identify. After they'd say 4 or 5 they were always stunned to learn that
only one process, carbon transfer or double transfer had been used. They
had no idea that such a wide spectrum of effects could be achieved out of
one process.
And what they saw did not even include full tricolor prints nor photoceramics.
Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada
http://www3.nbnet.nb.ca/nadeaul/