Joe,
First off, I'd like to thank you for taking the time to write such a thorough and informative post. This is precisely the type of information I was looking for.
I have several questions regarding some of the points you make, and I've parsed your post to better organize my thoughts.
This is the traditional approach and assumes (rightfully so) that shadow detail is essential to the photographer's envisioned final print. However as we all know, there are many variations on the traditional approach, as was encouraged by Ansel Adams himself. In my case, shooting (or perhaps "striving for") dramatic portraiture, I aim to depart from the literal and produce high contrast images that some might say border on illustrations. In my very modest experience, this is done by pushing film to the limits. Thus, shadow detail gives way to a preference for skin tones and important highlights. I've found that tailoring the dynamic range of the negative to this particular effect gives the photograph a glow that seems almost surreal
I assume that the reason that you are achieving this effect is that you are effectively mismatching the camera density range to the papers exposure scale and the net effect is that you are increasing local contrast in the process. It has been over twenty years since I got into Ansel Adams writings very heavily and I don't recall that he spoke much about local contrast. He seemed to be pretty well entrenched in the box of overall contrast.
One can achieve this mismatch that I speak of in one of several ways. The first is what you alluded to in pushing the film to it's limits...that would expand the density range of the negative beyond the exposure scale of the paper... pushing the shadows down the scale and spreading the contrast in the mid and upper tonal scale.
The same thing can be accomplished by increasing the contrast grade through filtration or using a harder grade paper.
Had you posted the foregoing statement last night, perhaps I would've gotten some sleep! I just spent the better part of the last few hours trying to figure out why "Print A" (print exposed for 11s @ f/8 with filtration #4) didn't have identical skin tones to "Print B" (print exposed for 22s @ f/11 with filtraion #5).
I think that if you review the literature on your enlarger, you will find that Saunders advises that exposure time remains constant for grade one to grade four...above grade four the times increase. I own a 4550 VCCE EXLG and this hold true on my enlarger.
I'm using a Saunders VCCE 4550 enlarger, and I paid a hefty sum for it after the sales rep gave me a run down of it's "magical properties" of Variable Contrast Constant Exposure. Yea... "Constant Exposure" my foot!
Point addressed above.
Could you recommend a rule of the thumb so to speak that would help give me an idea of the shift in tone with added filtration? Perhaps some empiracle formula or percentage?
While this doesn't follow Ansel Adams teachings, I recommend that you buy a Stouffer calibrated step wedge and determine the exposure scale of your paper at various filtration grades. Once you have determined the paper characteristics, you will know what a given negative density range will perform in what way on the paper at a given contrast grade.
Also, in what proportion would you say that "upping the contrast filtration" makes the "lights lighter" to making the "darks, darker" and vice-versa ?
While this will seem to fly in the face of what has been said by some here, my experience with the Saunders enlarger that you use indicates that once the high tonal values are established through the exposure time by the enlarger they do not shift much at all from grade one to grade four. The low values will become more pronounced as contrast grade filtration is increased. In other words the papers scale will shorten as contrast filtration is increased. The shortening predominantly occurs in the lower tonal scale. That is what my experience indicates. It has been verified by densitometric evaluation of the materials.
This same result holds true in my Durst condenser enlarger with contrast printing filters too.
Might I ask that you elaborate on this? Perhaps with an example (step by step).
Thanks again for taking the time and for your insights.