Agreed. An incident reading ignores the reflectivity of the objects in the scene, thus rendering them in their "true tonality" - assuming the film or media has sufficient range.Originally Posted by esearing
I don't know that we can actually determine this. I'm not clear whether Helen's spot reading was of a maximum-black area of the wet pavement, or of a reflective highlight area. That makes a huge difference in how one would interpret the reading. If the spot reading was of a highlight in which detail was to be retained, one might open up 2-3 stops, for example. If of a black area, the adjustment would be in the opposite direction - closing down 3-4 stops, perhaps.Originally Posted by esearing
The key point to remember is that a reflective reading gives the exposure needed to render the area being read as a middle gray (e.g. Zone V). Assuming you know accurately what area is being measured (as you would with a spot meter), you can then adjust the suggested exposure to "place" that value where it should be (or, where you want it), and everything else falls wherever it will accordingly. With B&W films (some responding better than others), you can adjust development to either expand or contract the contrast range for the desired effect. Naturally, that's not really possible with color film. The BTZS and Zone System methods are simply two different approaches to metering and development to achieve the desired result.