We present a new method for the calibration of inhomogeneous irradiance or
illuminance meters. Using this method, a lux meter equipped with a mosaic f
ilter was calibrated with an estimated uncertainty of 0.15 % (1 sigma). A p
reliminary illuminance comparison has been performed between the new scale
and a lamp-based scale maintained at the Nederlands Meetinstituut Van Swind
en Laboratorium (NMi VSL). The observed difference is equal to the uncertai
nty of this comparison, 0.4 %.