Am I wrong in stating that the "zone system" is a matter of previsualizing an exposure prior to taking it, taking into consideration the detail recording range of the particular film being used (in B&W's case roughly a ten stop range between blocked up black and washed out white) - then, based on this knowledge, placing the subject into whatever "zone" you want to expose it for, keeping in mind that the highlight and shadow zones will also be shifted (Or, in Ansel's case, placing the shadows in zone 1 to 2 as to not block them up, the developing for detail in the highlights - which works fine for NEGATIVE sheet film, but impossible for roll film....which may be why the Zone system has become this "mysterious monster" - exposing for the shadows and developing for the highlights works for negs because density is built up in highlights before it's built up in shadows - but the opposite is true with transparency film...the rule there is to expose for the highlights and let the shadows fall where they may (or adjust the lighting for the shadows) - the reason being that washed out highlights with transparencies will be forever that - washed out - there's no density there to correct. The zone system is based on the knowledge of the recording and print media's tonal range and contrast range, placing the exposed image within that range to achieve the desired result. this will differ depending on the materials used. the classic "10 stop zone system" is completely useless with transparency film (as the contrast range is reduced to about seven stops), as well as the axiom of "expose for the shadows, etc." is now completely reversed. Not being familiar with the digital format, I have to wonder what the contrast range of the medium is and whether it acts more like transparency film or negative film...? Whichever the case, it's a matter of determining the contrast range of the medium and dividing that into "zones", allowing a previsualization of the final image and the exposure placement of the elements of the composition. Photoshop has entered the venue as a confusing element, making it that much more difficult to determine what is actually "correct" - being that it has the ability to "correct" images to a previously unimaginable degree - but there's not substitute for a perfect exposure.