Measurement of light scattered by eye protection filters

In order to characterize the light scattered by eye protection filters a reduced luminance coefficient l* = L(s)/tauE is defined: L(s), luminance of scattered light, tau directional transmittance of the filter, E illuminance of incident radiation. The possibilities of measuring this quantity, which is specific for the material concerned [unit (cd/m(2))/lx = sr(-1)] are discussed, and a method is described which also fulfills the ophthalmological conditions; this is demonstrated for filters used in welding. By comparison measurements with an earlier American method, which gives the percentage of the scattered light, it is shown that a value l* = (1 cd/m(2))/lx is equivalent to 0.8% scattered light.