A method of signal harmonic error cancellation for a time of flight camera system (1, 3) characterised by the steps of: i) generating a source modulation signal which includes at least one identified harmonic frequency, and ii) adjusting the phase of the source modulation signal to provide a set of phase separated output signals which cancel error provided by the identified harmonic frequency, the output signals having phase offset values determined by the steps of: a. calculating the phase of the contribution of the identified harmonic to a measurement taken with a selected phase step value, b. determining a cancellation phase for the calculated phase of the harmonic contribution, c. determining a further phase step value which provides a measurement which includes a contribution from the identified harmonic, this contribution having a phase equal to the cancellation phase, d. repeating steps a-c to determine the phase values to be applied to the set of phase separated output signals, iii) modulating the output of the image sensor with the source modulation signal and illuminating a time of flight camera system image sensor with radiation being reflected from objects, said radiation being modulated by the first member of the set of phase separated output signals, iv) generating a time of flight camera measurement by integrating the output of the image sensor over a standard measurement time while only the first member of the set of phase separated output signals is used to modulate the illuminating radiation, v) illuminating the image sensor with radiation being reflected from objects, said radiation being modulated by only the next member of the set of phase separated output signals and integrating the output of the image sensor over the same standard measurement time while modulating the output of the image sensor with the source modulation signal to generate a further time of flight camera measurement, vi) repeating step (v) above for each remaining member of the set of phase separated output signals. i) generating a source modulation signal which includes at least one identified harmonic frequency, and ii) adjusting the phase of the source modulation signal to provide a set of phase separated output signals which cancel error provided by the identified harmonic frequency, the output signals having phase offset values determined by the steps of: a. calculating the phase of the contribution of the identified harmonic to a measurement taken with a selected phase step value, b. determining a cancellation phase for the calculated phase of the harmonic contribution, c. determining a further phase step value which provides a measurement which includes a contribution from the identified harmonic, this contribution having a phase equal to the cancellation phase, d. repeating steps a-c to determine the phase values to be applied to the set of phase separated output signals, a. calculating the phase of the contribution of the identified harmonic to a measurement taken with a selected phase step value, b. determining a cancellation phase for the calculated phase of the harmonic contribution, c. determining a further phase step value which provides a measurement which includes a contribution from the identified harmonic, this contribution having a phase equal to the cancellation phase, d. repeating steps a-c to determine the phase values to be applied to the set of phase separated output signals, iii) modulating the output of the image sensor with the source modulation signal and illuminating a time of flight camera system image sensor with radiation being reflected from objects, said radiation being modulated by the first member of the set of phase separated output signals, iv) generating a time of flight camera measurement by integrating the output of the image sensor over a standard measurement time while only the first member of the set of phase separated output signals is used to modulate the illuminating radiation, v) illuminating the image sensor with radiation being reflected from objects, said radiation being modulated by only the next member of the set of phase separated output signals and integrating the output of the image sensor over the same standard measurement time while modulating the output of the image sensor with the source modulation signal to generate a further time of flight camera measurement, vi) repeating step (v) above for each remaining member of the set of phase separated output signals.