Dimensional analysis of visual signals

The classical radiance-luminance parallelism of units for the measurement of emission and reception of flux applies when visual processing is modeled on principles of physics or engineering. “Energy” has a defined meaning in these disciplines: it is the time integral of flux; the time rate of transfer of flux has the dimension of power. Hence energy is appropriate only when light stimuli are delimited in time, else power is the applicable word. To conform to dimensional specifications in physics, energy models in vision would deal with packets of stimuli of fixed duration, not the time rate of excitation, and have magnitudes expressed in the form of the square root of the integrated squared spatial or spatio-temporal distributions.