Digital BW, The Print

http://www.luminous-landscape.com/tutorials/zone_system.shtml

Ansel's system centered on TRAINING THE EYE to previsualize and
control B&W from color scenes. It only SECONDARILY utilized densitometry.

Slightly knowing the man (a customer) and better knowing some of his
disciples, it was obvious that he attracted attracted anal retentive
types, some of whom became fine scenic photographers (as opposed to
portrait, journalistic, or illustrative), many of whom became
merchants in tourist galleries (as in Carmel, Moab, NYC). 

AA's B&W gospel was not the ultimate and his densitometry was just a
particular spin. 

Ansel's particular spin on Zone System was, in addition to his own
obsessive mindset, substantially due to the fact that films and papers
were not as predictable in his early days as they became in the
Sixties (the B&W materials...critical color still required testing,
batch-by-batch, but skilled color photographers worked VISUALLY,
developed advanced VISUAL skills, just as Ansel taught in B&W) . 

Ansel elected to use densitometry when it became available. His early
prints weren't technically as wonderful by modern standards as were
the early images themselves, due to his aspirations, not to early lack
of densitometer...if you've seen his life's work in hundreds of
original prints you see that. 

Ansel's primary technical gift to us (facilitated by Minor White, the
better teacher) was PREVISUALIZION of zones: Learning reliably to see
specific zones of grey in color scenes, controlling them in exposure,
processing, and printing.  

The beginning and center of that process was learning to identify Zone
Five...which EVERYBODY in the 60s and 70s had to learn visually,
whether or not they ever heard of Zone System or Ansel: Basic proper
use the TTL meters in the various FTNs, F1s and Spotmatics...which are
designed specifically for Zone Five (same as Kodak's grey card).