Interference filter calibration for vision research

The radiant flux (F) transmitted by bandpass interference filters of similar type is approximately proportional to the product of peak transmittance (tp) and half-height bandwidth (Wh). A study of 297 filters of varied design (1-, 2-, 3-cavity), the collections of six vision laboratories, showed that this relation was not accurate across all filters. However, a simple function, incorporating Wh and another bandwidth Wi at a lower transmittance t, predicts F with a precision that is ample (+/- 5%) for most psychophysical research. This function provides a rapid means of calibration. Bandwidth errors caused by 2- and 3-cavity filters are discussed as well as their luminous 'blocking' efficacy.