What is watts per gallon?

If I have 2 x 100 watt incandescent that is 200 watts.

If I have 2 x 38 watt flourescent tubes that is 76 watts.

The flourescent tubes output much more light in the correct spectrum.
Shouldn't we be measuring the light level at the required wavelength rather
than just measuring the input power required by the illumination source?

Even forgetting the wavelength, surely we should be measuring foot-candles
or lumens rather than watts?


Graham.