The accurate way to determine where the highs fall is to measure them with a spot meter.
Originally Posted by mark
An example of how this might work and the effects is as follows:
Lows values measure 4 seconds exposure.
High values measure 1/15 second exposure
One would think that normally this would represent a six stop brightness ratio. But when the additional reciprocity is factored in we now have the low values exposed for 8 seconds (proper exposure accounting for reciprocity)and the highlights exposed for 8 seconds (overexposed by seven stops). This pushes the highs up the curve by seven stops. So that we now have a different scene brightness ratio then a simple meter reading would indicate. That is why the departure from normal development procedures in reciprocity is reduced development.