a) Measure the luminous transmittance τv according to 7.1.2 (and other transmittances to be checkedas described in 7.2 to 7.8) and wide angle scatter according to 7.9.b) Expose the front surface of the filter to radiation from the lamp.c) Ensure that the angle of incidence of the radiation on the specimen surface is essentiallyperpendicular.d) The distance from the axis of the lamp to the nearest point on the sample shall be (300 ± 10) mm.