I've been shooting landscapes with 4x5 Tmax (100 and 400) over the past year or so using the zone system rather loosely. I would now like to test the film and my processing to determine effective film speed, n+1, n-1, etc. My question is this: should I simply follow the procedures laid out in Adam's The Negative, the n hunt around for a shop with a densitometer, or should I use the Darkroom Innov ations BTZS film testing method? Are the two really "alternate" ways of determi ng the items noted above, or am I misunderstanding the nature of the BTZS system ? Thanks in advance, I truly appreciate the benefit of your experience.