Chuck's comments got my attention and I had a few minutes to poke
around. It appears DXO tries to eliminate any camera processing out of
there assessment of ISO where as DPrev used the camera and compared the
exposure to a Sekonic meter--middle grey matched. I wonder if some
gain is introduced somewhere resulting in the difference. DXO also
agrees with the Moose Conjecture that the ISO dial is very possibly
linked to some manufacturers leaving in some headroom as not to clip
highlights.---see below.
http://www.dxomark.com/index.php/eng/Technologies/Measurement-definitions/ISO-Sensitivity
DXO gives some info on their protocol---much different than DPrev and
uses LED's. I'm clearly missing some imp't points and nuances. Not
sure which is more useful. Before I attempt any more thought on the
matter, will go and get about 16 oz of strong Melior coffee.
Mike
http://www.dxomark.com/index.php/eng/Technologies/Testing-protocols/ISO-Sensitivity-protocol
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