Bill -

Yes, you are correct about the step wedge readings and exposure, it's kind of a relative thing because you can see the information in the graphed data. Metering and exposure in the field is more critical and demands consistent methods if you're going to get consistent results, and it's a whole lot more challenging out there than it is in the darkroom! Whether a person's exposure index for a film matches box speed, or is half or twice box speed is irrelevant. The amount of light hitting the film needs to be correct and consistent regardless, and consistent testing will support good results.

Peter Gomena