Units and Useful Range in Photo-electric Colorimetry

Abstract

THE major practical point in dispute is not "how far the useful range extends towards both ends of the scale" (though we believe this to be narrower than many published figures imply), but whether the proposed new unit fulfils any useful function not already covered by the old ; and on this issue we have nothing to add to our original arguments. We would ask only that anyone who still prefers to use the ‘half-‘value should also, for the convenience of the reader, give the equivalent E (1%, 1 cm.) value.