I'll leave it to Fred Newman to comment in more depth, but I believe that Mark is quite right. The metering done in BTZS is with the ASA set at 100; one is simply reading the values of the highlights and the shadows without any attempt to use such metered values to calculate the exposure. Based upon the testing of one's film, one uses the results to determine the SBR AND most importantly, the EFS at the SBR in question. Using the EFS ( which is then set into the meter in place of the ASA 100 ) allows one to use the shadow value(s) to correctly expose the negative. What is as yet unsaid is that one can quickly learn to use the placement of the incident meter so as to render the shadows however one desires, i.e., to obtain more or less shadow detail. As Mark writes, there are points to be made for the classic zone system using reflected metering, and BTZS using incident metering. In either case, testing of one's materials is integral to obtaining the "correct exposure". Furthermore, experience and experimentation will allow one to use either system to use "creative" exposure so as to obtain prints that reflect one's sense of how the scene in question is to be interpreted.
I use BTZS with the ExpoDev program, and I would never go back to the Zone System. However, again as Mark correctly infers, use whatever "system" of film exposure and development works for you. One is not "better" than the other. Indeed, if one learns to develop by inspection, simply expose for the shadows at a film speed that yields good shadow detail, and pull the negative from the developer when the highlight details are "right"! Grist for another mill.....
Last edited by Mahler_one; 05-10-2012 at 12:23 PM. Click to view previous post history.