The relative spectral sensitivity of the materials shown here
is based on the impact on oil paintings (reference value:
100 percent). So watercolours, at 485 percent, are nearly five
times more at risk than an oil painting. The illuminance on
the object is 200 lux – a compromise between the brightness
needed for the visual task and the conditions required for
conservation; the illuminance on very sensitive objects should
not exceed 50 lux.