A light emitting diode controller for a system comprising a plurality N of LED channels (602-1,... 602-N), the light emitting diode controller comprising: channel select circuitry configured to: sequentially select one of the N LED channels (602-1,..., 602-N) and drive said selected channel at a probe modulation frequency (fp); drive the remaining N-1 LED channels of the N LED channels (602-1,..., 602-N) at a selected nominal modulation frequency (fnom) of one or more nominal modulation frequencies; detection circuitry configured to: receive a composite brightness signal corresponding to brightness signals from the N LED channels (602-1,..., 602-); filter the composite brightness signal; and generate a selected brightness signal corresponding to a brightness of the selected LED channel at the probe modulation frequency from the filtered composite signal; and error processor circuitry configured to: compare the selected brightness signal to user defined and/ or preset photometric quantities; and generate a control signal for adjusting the brightness of the selected LED channel. channel select circuitry configured to: sequentially select one of the N LED channels (602-1,..., 602-N) and drive said selected channel at a probe modulation frequency (fp); drive the remaining N-1 LED channels of the N LED channels (602-1,..., 602-N) at a selected nominal modulation frequency (fnom) of one or more nominal modulation frequencies; detection circuitry configured to: receive a composite brightness signal corresponding to brightness signals from the N LED channels (602-1,..., 602-); filter the composite brightness signal; and generate a selected brightness signal corresponding to a brightness of the selected LED channel at the probe modulation frequency from the filtered composite signal; and sequentially select one of the N LED channels (602-1,..., 602-N) and drive said selected channel at a probe modulation frequency (fp); drive the remaining N-1 LED channels of the N LED channels (602-1,..., 602-N) at a selected nominal modulation frequency (fnom) of one or more nominal modulation frequencies; detection circuitry configured to: receive a composite brightness signal corresponding to brightness signals from the N LED channels (602-1,..., 602-); filter the composite brightness signal; and generate a selected brightness signal corresponding to a brightness of the selected LED channel at the probe modulation frequency from the filtered composite signal; and receive a composite brightness signal corresponding to brightness signals from the N LED channels (602-1,..., 602-); filter the composite brightness signal; and generate a selected brightness signal corresponding to a brightness of the selected LED channel at the probe modulation frequency from the filtered composite signal; and error processor circuitry configured to: compare the selected brightness signal to user defined and/ or preset photometric quantities; and generate a control signal for adjusting the brightness of the selected LED channel. compare the selected brightness signal to user defined and/ or preset photometric quantities; and generate a control signal for adjusting the brightness of the selected LED channel.