Originally Posted by
xpatUSA
Beyond terse one-line statements, it will be well worth reading Section 3.5 of:
dougkerr.net/Pumpkin/articles/Secret_Life_Exposure_Metering.pdf
There we can learn exactly what exposure will be recommended by an incident-light meter. It is t/N^2 = C/(Es.S)
where t=shutter time, N=f-number, C= calibration constant=340 on my Sekonic, Es=illuminance of the light in lux and S=ISO setting on the meter, not the camera.
So let's say those kids are sitting in partial shade at say 2000 lux and Evert sets say 400 ISO because the kids are moving a bit.
In it's tiny brain, the meter decides that t/N^2 is 4.25x10^-4. From that, in camera exposure terms, my meter will recommend about 11EV. Since some people have no idea what that means, my meter also has a handy-dandy circular slide-rule scale that sets shutter speed against aperture. If, like Bill I decide f/4, the meter's recommendation on that scale is 1/125 sec for f/4.
None of the above has anything whatsoever to do with the resulting histogram in the developed image which, as George implies, has to do with the reflectivity of the various parts of the scene (dare I say Zones?) and the photographer's adjustments to the meter's recommended exposure.