Gravitational redshift is conventionally believed to be the result of the loss of energy of photons as they emerge from a strong gravitational field into a field of lesser strength. Conversely, gravitational blueshift is believed to be the result of an increase in energy of photons as they move into a stronger gravitational field from a field of lesser strength. I will argue that gravitational redshift is caused by time dilation of the source of radiation at the gravitational body. The redshift of the photons emitted by the source accounts in full for the measurement of redshift of those photons in a lesser gravitational field. The obverse works for the measurement of gravitational blueshift. The frequency of the photons received in a stronger gravitational field is measured to be greater than the emitted frequency because of time dilation of the receiver. The measured blueshift is illusory and is a measurement artifact. The frequency of a photon is not changed as the photon moves within a gravitational field to either a weaker or a stronger field.