Another experiment, this time with the D300. Four exposures, 2 manual, 1 each normal and LV, 2 aperture, ditto. I used my discretion for the manual exposures but they were virtually identical except that the LV shot was marginally darker (the histograms shifted minimally but noticeably). The same lack of substantial exposure shift was true of the aperture priority exposures except in this case the LV was equally marginally lighter. The difference in each case I would guesstimate to be in the realm of a Just Noticeable Difference, however that may be quantified.