A method for authenticating a value article, wherein the method comprises the steps of: providing the value article comprising a luminescent material; providing an exciting light source, an optical filter, a photodetector, a signal manipulation circuit, which is an electronic frequency filter and an amplifier; exposing the luminescent material of the value article to modulated light produced by the exciting light source at a predetermined pulse modulation frequency, wherein the luminescent material exhibits a frequency response during emission of radiation therefrom, wherein the frequency response of the luminescent material includes the predetermined modulation frequency; filtering radiation comprising light from the exciting light source and emitted radiation from the luminescent material using the optical filter to produce filtered radiation comprising emitted radiation from the luminescent material; detecting the filtered radiation using the photodetector to produce a detected radiation signal; electronically manipulating the detected radiation signal using the signal manipulation circuit comprising selectively attenuating portions of the detected radiation signal at the predetermined modulation frequency of the exciting light source with respect to desired portions of the detected radiation signal using the electronic frequency filter to produce a filtered electronic signal to reduce an effect of light from the exciting light source on an authentication determination based on the filtered electronic signal; amplifying the filtered electronic signal with the amplifier after the detected radiation signal is electronically manipulated to produce an amplified electronic signal; and converting the amplified electronic signal or data derived therefrom to an authentication output wherein the luminescent material exhibits a frequency response during emission of radiation therefrom, wherein the frequency response of the luminescent material includes the predetermined modulation frequency, and wherein selectively attenuating portions of the detected radiation signal at the predetermined modulation frequency comprises selectively attenuating portions of the detected radiation signal produced by the luminescent material at the predetermined modulation frequency. providing the value article comprising a luminescent material; providing an exciting light source, an optical filter, a photodetector, a signal manipulation circuit, which is an electronic frequency filter and an amplifier; exposing the luminescent material of the value article to modulated light produced by the exciting light source at a predetermined pulse modulation frequency, wherein the luminescent material exhibits a frequency response during emission of radiation therefrom, wherein the frequency response of the luminescent material includes the predetermined modulation frequency; filtering radiation comprising light from the exciting light source and emitted radiation from the luminescent material using the optical filter to produce filtered radiation comprising emitted radiation from the luminescent material; detecting the filtered radiation using the photodetector to produce a detected radiation signal; electronically manipulating the detected radiation signal using the signal manipulation circuit comprising selectively attenuating portions of the detected radiation signal at the predetermined modulation frequency of the exciting light source with respect to desired portions of the detected radiation signal using the electronic frequency filter to produce a filtered electronic signal to reduce an effect of light from the exciting light source on an authentication determination based on the filtered electronic signal; amplifying the filtered electronic signal with the amplifier after the detected radiation signal is electronically manipulated to produce an amplified electronic signal; and converting the amplified electronic signal or data derived therefrom to an authentication output wherein the luminescent material exhibits a frequency response during emission of radiation therefrom, wherein the frequency response of the luminescent material includes the predetermined modulation frequency, and wherein selectively attenuating portions of the detected radiation signal at the predetermined modulation frequency comprises selectively attenuating portions of the detected radiation signal produced by the luminescent material at the predetermined modulation frequency.