There seem to be numerous discussions regarding reported EXIF data that is not reliable: ISO's of 1, Av's of 2.8 and Tv's in the tens of thousands.
Using the histogram for benchmarking will help clarify these matters.
While a full discussion of the Zone System, 18% reflectance and histograms is available from numerous other sources, the relevant concept is that the histogram can be used to provide points of reference from which more accurate conclusions can be drawn.
One simple example: ISO bracketing in continuous mode with increasing exposures will show the histogram incrementing with each consecutive exposure, even though the EXIF data remains the same for two or three exposures. Through interpolation, more accurate ISO values can be determined for the intermediate exposures.
HTH,
