In this article, a new method for measuring a total spectral radiance factor of a FWA-treated sample illuminated by a specific standard illuminant is introduced. The method replaces an unstable real fluorescent standard by a bi-spectral luminescent radiance factor data, which works as a virtual fluorescent standard (VFS) by knowing spectral intensity distributions of illuminations applied to the sample. The method utilizes two illuminations I-1 and I-2 whose relative spectral intensity distributions are different from each other and synthesizes a virtual illumination presenting the identical fluorescent spectral radiance factor to that presented by the standard illuminant with the VFS of the specific bi-spectral luminescent radiance factor by linearly combining 11 and 12 with the suitable weighting factors. The applicability of the method is examined in principle by comparing ISO brightness and CIE whiteness index of fluorescent standard paper as a test sample obtained by this new method to the assigned values. (c) 2007 Wiley Periodicals, Inc.