Quote Originally Posted by Stephen Benskin View Post
... the measurement made is no longer of the average scene luminance which it has been stated above is that on which the photographic constant P, as defined later, is based. In this case, it would be necessary to know which part of the scene to select to obtain a measurement equal to the average, or alternatively, a measurement of either the maximum or the minimum luminance could be made, but then a different value of the constant P would have to be determined and used.
I think this can be loosely translated... "If we make a spotmeter, then photographers will have to know where to point it."... "and if they point it at a shadow or a highlight, they'll have to know where to set the dial"