<P> A source radiating a power of one watt of light in the color for which the eye is most efficient (a wavelength of 555 nm, in the green region of the optical spectrum) has luminous flux of 683 lumens . So a lumen represents at least 1 / 683 watts of visible light power, depending on the spectral distribution . </P> <P> Lamps used for lighting are commonly labelled with their light output in lumens; in many jurisdictions this is required by law . </P> <P> A 23 W spiral compact fluorescent lamp emits about 1,400--1,600 lm . Many compact fluorescent lamps and other alternative light sources are labelled as being equivalent to an incandescent bulb with a specific wattage . Below is a table that shows typical luminous flux for common incandescent bulbs and their equivalents . </P> <Table> Electrical power equivalents for differing lamps <Tr> <Th> Minimum light output (lumens) </Th> <Th_colspan="3"> Electrical power consumption (watts) </Th> </Tr> <Tr> <Th> Incandescent (non-halogen) </Th> <Th> Compact fluorescent </Th> <Th> LED </Th> </Tr> <Tr> <Td> 200 </Td> <Td> 25 </Td> <Td> 3 - 5 </Td> <Td> </Td> </Tr> <Tr> <Td> 450 </Td> <Td> 40 </Td> <Td> 9--11 </Td> <Td> 5--8 </Td> </Tr> <Tr> <Td> 800 </Td> <Td> 60 </Td> <Td> 13--15 </Td> <Td> 8--12 </Td> </Tr> <Tr> <Td> 1,100 </Td> <Td> 75 </Td> <Td> 18--20 </Td> <Td> 10--16 </Td> </Tr> <Tr> <Td> 1,600 </Td> <Td> 100 </Td> <Td> 24--28 </Td> <Td> 14--17 </Td> </Tr> <Tr> <Td> 2,400 </Td> <Td> 150 </Td> <Td> 30--52 </Td> <Td> 24 - 30 </Td> </Tr> <Tr> <Td> 3,100 </Td> <Td> 200 </Td> <Td> 49--75 </Td> <Td> 32 </Td> </Tr> <Tr> <Td> 4,000 </Td> <Td> 300 </Td> <Td> 75--100 </Td> <Td> 40.5 </Td> </Tr> </Table>

1 lumen per square metre is the same as