Originally Posted by ajbaudio
On lights: As an electrical engineer and amateur photographer, I must point out that the Watt is unit of measure for physical power. Watts can tell you how much power a light may consume, but its cannot tell you exactly how "bright" the light will be. For example, a 100 W incandescent light bulb may appear brighter or darker to the human eye than a 100 W halogen light bulb, depending on bulb type, fixture/enclosure, etc.
Since photons don't ride bicycles, I won't drag this too far into the physics/math world, but the problem here isn't the watt as a unit of measurement, its how the watts are measured. photons all have an individual associated energy and from a given flux of photons with a given wavelength, the amount of power (watts) incident across a surface can easily be calculated or measured if you're a bit more suave.
that said, it was easier to standardize measuring the power consumption of bulbs back in the whatever years, so that's likely why we're stuck with it now.
