Quote Originally Posted by sanking
The important thing to understand about the scene you describe is that neither a reflected reading nor an incident reading will give you the correct exposure to reproduce the tonal values as you want them without interpretation.
I agree completely. Anytime you are shifting tones away from a direct approximation of the original scene requires interpretation. Never said otherwise.

Quote Originally Posted by sanking
One option is to go to one of the shadow areas of the scene and take a meter reading at that spot, note how much this EV values differs from the EV value of the first reading, and subtract from the SBR of 5 to give you a new SBR value, which could be 3 or 4. If there is not a real shadow area large enough to use for the reading you can simulate the shadows by shading the cone of the meter, take a reading, and then do the same calculation as above. Base exposure on an average of the shadow (or shaded) reading and the reading taken in full light. Or you could just double the EFS of the film and make the exposure based on the shadow reading.
Thanks for this technique - this is what I'm asking about. However, I'm not sure about it. I had no shadow areas with the sand pattern or the rock art. I guess I'm not visualizing what you are suggesting to do - here's what I think you are suggesting:

1) I have a subject with no shadow areas, one that is of low contrast.
2) Take a reading in the sunlight with the incident meter at the subject.
3) Take a second reading in the shade of my hand.
4) Subtract the two readings.
5) Exposing with the average reading.

This seems like a kludge. Is there a basis in the BTZS method for this, or just something that has been found to work fairly well? It seems like you could get a lot of variation based on how much you cover the meter sensor with your hand.