A method to correct measurement error in a resonance energy-transfer assay, including exciting anti-Stokes photoluminescent donors with at least one wavelength of light which is greater than an emission wavelength of acceptor molecules; measuring emission at the acceptor's emission wavelength and which differs from the donor's emission wavelength in at least two different time windows; a first time window within the time window defined by the excitation light pulse and a second non-overlapping time window which follows the first time window; and correcting the emission signal, which includes signals originating from non-radiative and radiative energy transfer, within the first time window by estimating the ratio of the signals from non-radiative and radiative energy transfer or the signal originating from radiative energy transfer using at least one emission signal measured in the second time window.