Quote Originally Posted by Diapositivo View Post
With an incident meter under even illumination you only meter one value and have no idea of the degree of "inner contrast" of the scene.
In Phil Davis' version of the Zone System (Beyond the Zone System), he takes advantage of the characteristics of the incident meter to make two readings with an incident meter, one in the main light and one in a shadow area, and uses the difference in those readings to determine a subject brightness range, then adjusts exposure and development time accordingly. It's a great system, relatively simple, and works very well. In my book it's a better system for a novice than expecting a novice to guess at how to 'place' zones with a spot meter.

Of course there are instances where it's logistically impossible to make a shadow reading in the scene being photographed, but there are ways to make a substitute shadow reading. This is illustrated in Davis' books.