Under direction from Congress to re-examine the current labels, the FTC is announcing a final rule that will require the new labels on light bulb packages. For the first time, the label on the front of the package will emphasize the bulbs’ brightness as measured in lumens, rather than a measurement of watts. The new front-of-package labels also will include the estimated yearly energy cost for the particular type of bulb.
This will allow one to make an easier comparison of bulb’s brightness, but it should be noted that lumen is the unit of luminous flux, which is the brightness as perceived by the human eye. The eye’s efficiency peaks at about 550 nm, and tapers off at the red and blue ends of the spectrum, and the lumen compensates for this. In other words, it’s not the actual amount of visible light energy given off, it’s how bright it looks. This is a trick used in the past by laser pointer manufacturers, when they started coming out with shorter-wavelength (i.e. redder or non-red) devices. Because the eye was more sensitive, they appeared brighter, even though the power was actually smaller. 1 mW of green can be as bright as ~5 mW of red, depending on the exact wavelengths involved.