Nice illustrations Mr. Porter...thanks. I agree that averaging the highlight values might well be the best way to proceed. As noted below, it is wonderful that you are obtaining great results using your metering methods. Nicely done.
I think one must recall that incident metering via Phil Davis/BTZS does NOT involve only one meter reading. I respectfully state that those who are commenting about the BTZS system as being based on a single highlight incident meter reading are not accurately reporting on the BTZS system/ method. Please consider avaiing yourselves to the material available on the BTZS system and incident metering.
If those who are using only a single incident shadow or highlight reading are obtaining the results that they desire...well done! I have nothing further to add or suggest. Add a stop, subtract a stop...heck, who cares if your results are as you desire.
Mark: In his text Phil David clearly states that if absolutely necessary, basing an exposure on a single highlight reading will be incorrect unless one INCREASES the exposure. Without such action, the meter will render the single highlight reading as middle grey. If one MUST base one's exposure on a single shadow reading then one must decrease the exposure so that the tones are moved down from middle gray. Increasing the exposure will raise the highlights to a more "correct value"....and will of course increase the shadow exposure. As to the 18% illumination and 5 stop range that Mr. Davis alludes to: Everything is very well explained starting on page 131 of the 4th edition of his book. The 5 stop range is based upon studies that are well detailed. Of course, feel free to differ from Mr. Davis's conclusions. You are entitled to your opinions and surely such are based upon sound experimental or empiric data as reflected in your negatives and prints. I am very pleased that your "system" works for you, and that most of your film exposures and prints meet all of your expectations. Well done. As to your comments about teachers: All teachers synthesize material and interpret such. Students can decide to reject or modify the material presented. However, if they do so then such changes should be accompanied with illustrations and information as to the methods that they have used to deconstruct the information presented, and the data illustrating the validity of the reinterpretation that they have applied to the chemical and physical realities of the photographic process. Of course, if you are at the stage that teachers cannot offer you any useful information and advice then you have progressed far beyond what must of us here have attained. Again, well done!
For emphasis: The BTZS system depends upon two readings, highlights and shadows. The zone system depends upon two readings-highlights and shadows- with appropriate placement so as to determine the time of development. In both systems one can manipulate exposure so as to render the negative with the tones that one desires. In both "systems" a single reading will not suffice.
If one wants to use a single shadow reading then another approach might be developing by inspection in which one will expose for the shadows and then determine development by the appearance of the highlights under a green safe light in the darkroom. DBI is fun, and many will eventually acquire the necessary visual skills. Moreover, one can learn to develop 4-6 sheets of film at one time.
Exposing for the highlights was a method that at one time the late Fred Picker advocated. Perhaps those who have studied with Fred can comment.
Andreas-I am sorry that you are having some problems with the BTZS system. As I offered, we can discuss any issues via PM. I and others are ready to help.
Some are successful using reflected metering and the ZS, others using BTZS and incident metering, and still others use whatever "system" they have devised based upon their material and metering methods that work for them.
Now it's time to once more go into the field and take some photos. Use whatever "exposure system" works for you; if you are getting the results that you desire, who cares.
Last edited by Mahler_one; 03-02-2013 at 11:23 PM. Click to view previous post history.