Different books say different things regarding testing for the highlights in the zone system. The Kodak book Advanced Black and White Photography suggests testi ng for a zone 7 density of 1.05. Most other books say to test for a zone 8 densi ty of 1.30. With developers that produce a straight line, these two densities fa ll into place: when zone 8 is at 1.30, zone 7 is near 1.05. With D-23, however, this is not so. D-23 produces a shoulder for me, which throws these two densitie s off. With HP-5+ if zone 8 is at 1.30, then zone 7 is too high. If zone 7 is at 1.05, then zone 8 is too low. If I use zone 8 as the standard, 7.5 min in D-23 1:1 is an N-2 development, but if I use zone 7 as the standard, the same develop ment time is N-1. So is 7.5 min. an N-1 or an N-2 development?
I am wondering, is it more important to get zone 7 or zone 8 in the right place. I would think zone 7 is more important, since this is the highlight with full d etail, and when metering, one places the important high value on zone 7, not zon e 8. What do you think? Should I test for zone 7 or zone 8 with a developer that produces a shoulder?