A reader asks:

 There’s no magic about the date of time change. Some people with SAD, or those with the less severe winter doldrums, begin to feel down well before the time change, while others feel well till much later in the season.


Color Temp

The term “full spectrum” is not precisely descriptive of the light quality of a unit. More specific is the color temperature (e.g., 3700K, 5000K or 6500K). All these color temperatures can be effective in light therapy or for task lighting. The higher color temperatures contain more short wavelengths, i.e., the blue component of white light. The photons emitted by fluorescent bulbs, whether the tubular or screw-in type, are no different from one another at a given color temperature.

Proper Light Level

What is most important in selecting a light box is to ensure adequate light level, smooth diffusion of the light through a filtering screen, and positioning of the light at and above (NOT below) the line of sight. A given unit might be used effectively for task lighting or light therapy. For task lighting, it is important to ensure that the light level can be switched up or down, since one would not want to maintain maximum light therapy intensities for long durations during the work day.