Archived posting to the Leica Users Group, 1997/07/14

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: Re: R8 metering (technique)
From: pgs@pa.dec.com (Patrick Sobalvarro)
Date: Mon, 14 Jul 1997 16:22:23 -0700

   Date: Mon, 14 Jul 97 20:15:04 +0200
   From: Erwin Puts <imxputs@knoware.nl>

   Now the assumtion behind the 18% is the idea that the average
   distribution of light and dark tones in a scene is equal to 18%
   reflectance of the incident light...

   In reality the distribution of light and dark scenes follows the
   standard statistical Bell curve. If you adopt this in the exposure
   calculations, then the average scene has a reflectance value of
   13%, which is more realistic...

Hello Erwin, I found these sentences hard to understand, and was
wondering if you could explain this further.  Are you saying that,
while the ensemble average reflectance over all scenes that people
might be expected to photograph is 18%, the mode (the reflectance
value that the largest number of scenes has) is in fact 13%?  But this
is not characteristic of a "bell" curve, for which mode and mean are
the same.