BS ISO 26723:2020 pdf free.Plastics - Determination of total luminous transmittance and refl ectance. BS ISO 26723 5.1 The apparatus shall consist of a stabilized light source, an associated optical system, an integrating sphere with ports, and a photometer comprising a photo-detector, signal processor and display unit or recorder (see Figure 1).， 5.2 The light source and the photometer shall...