The overhead, ambient lighting was provided by two
luminaires perpendicular to the test lamp, each containing
two 1.2m (4 feet) T-8 fluorescent lamps, covered
with plastic diffusers. They were positioned to provide
diffuse, ambient non-polarized lighting 2m above the
reading surface, each 1m on either side of the reading
surface. The illuminance provided by this lighting at the
center of the reading surface, 200mm toward the lamp
from the test subject was 480 lux. This illuminance can
be considered the high end of the recommendations
given in IES Lighting Handbook (1981), which recommends
200–500 lux for reading tasks at office desks