Table 1.

Photopic illuminance and human retinal photopigment-weighted illuminance measures from the LE-eBook device and light reflected by the printed book

DevicePhotopic luxCyanopic luxMelanopic luxRhodopic luxChloropic luxErythropic lux
Print book*0.910.450.650.680.810.92
  • Radiometric light readings were taken in the same dim background room light conditions and from the same distance (38–40 cm). The LE-eBook was set to the maximum brightness setting.

  • * Illuminance in the printed book condition was measured from the ambient room light emitted by the ceiling fixtures and reflected by the book, using the recently proposed light measurement strategy that takes into account non–image-forming retinal responses to light (see Methods).