Quote Originally Posted by chuck94022
Actually I thought they were logarithmic...
Alternatively you could measure it against a calibrated luminance ...
The EV scale on my Sekonic goes 3, 4, 5, ... ,18. Logs would run
0.0, 0.3, 0.6 and on. Each of those logs is double the light as is
each suceeding EV. The log of 2, twice as much light, is 0.3.
For some reason the scale does not read in logs;
convention I suppose.

Measureing against a light source I think a good idea. The
source need not be calibrated as we are not interested in the
absolute value of the light. A meter which measures the light
intensity in lamberts, or foot candles, or ... , likely should
use a standard as light source. We make our correction
when setting the ISO to this or that on our meters
for our personall EI.

The inverse square law as applied to a point light source in
the vacuum of deep space would be extremly accurate. Something
terrestrial of that sort might be plenty good enough. Dan