Some reviews and other forums and this from LumiGrow site....
Similarly, light meters that measure in “lux” tell us very little about a lamp’s plant-growing power. The light sensors in lux meters have their own spectral response curves which may over- or under-measure light at various colors. This is why lux meters usually have different settings for “sunlight,” “fluorescent” and “incandescent” lamps. Again, because lux meters are meant for measuring the amount of light usable by humans, they don’t tell us anything about how plants will respond. Plant biologists define light in the 400nm to 700nm spectral region as “photosynthetically available radiation,” or
PAR. The unit for measuring PAR, micro-mols per second (μmol/s), indicates how many photons in this spectral range fall on the plant each second