The only thing I'd add is that the watts that equipment labeling and sales literature are talking about is the electrical power that is delivered to the lamps. This is different than the irradiance of the energy that is received by the skin or by a detector.
Watts of electircal power are just volts X amps, and don't necessarily translate into W/m^2 of UVR that the tanners' skin receives. And it certainly doesn't address the W/m^2 (or W/cm^2) of UV light at the useful and desired wavelengths. Irradiance which is measured in W/m^2, or some factor of 10, and watts of electrical power are apples and oranges. And that's what Jerry was trying to get across instead of making things as clear as mud like I'm probably doing.
But the more electrical watts that are used to power lamps, the more radiant energy those lamps can produce, and potentially, the more W/cm^2 of irradiance that can be received by the skin surface from those lamps . That fact is simple physics. Like everyone has already said though one way or another, lamp and reflector geometry, filtering, and other factors such as cooling all play a role in determining how much of the desired W/cm^2 is actually able to be received. And this is true for both HP and LP systems. |