Comparisons of three practical field devices used to measure personal light exposures and activity levels.
This paper documents the spectral and spatial performance characteristics of two new versions of the Daysimeter, devices developed and calibrated by the Lighting Research Center to measure and record personal circadian light exposure and activity levels, and compares them to those of the Actiwatch Spectrum (Philips Healthcare). Photometric errors from the Daysimeters and the Actiwatch Spectrum were also determined for various types of light sources. The Daysimeters had better photometric performance than the Actiwatch Spectrum. To assess differences associated with measuring light and activity levels at different locations on the body, older adults wore four Daysimeters and an Actiwatch Spectrum for five consecutive days. Wearing the Daysimeter or Actiwatch Spectrum on the wrist compromises accurate light measurements relative to locating a calibrated photosensor at the plane of the cornea.
Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180.
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Figueiro
Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180.
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Hamner
Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180.
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Bierman
Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180.
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circadian system; light exposure; photometric devices; rest/activity patterns