Photometry and Colorimetry of Fluorescent and other Electric Discharge Lamps

After reviewing the progress from visual to photoelectric heterochromatic photometric techniques which are in accordance with C.I.E. recommendations, a fairly detailed description is given of the design and performance of a new dispersion and mask type of photoelectric C.I.E. average eye, colorimeter, and spectral band apparatus. Reference is also made to liquid filters for use with photocells to give approximations to C.I.E. average eye response and to a new design of universal photoelectric photometer for use with them. Methods are described of ensuring accurate electrical measurements when setting up tubular fluorescent lamps in photometers, together with details of the precautions which must be taken because of their characteristics and as the result of the special photometric integration problems which they introduce. Finally, mention is made of the precautions which must be taken when measuring with photoelectric illumination meters the illumination from such lamps at low mounting heights, and reasons for deprecating the practice of specifying the colour of these lamps in terms of colour temperature.