The results of two experiments in terms of the subjective response to the changes in brightness on the desk with time and that to changes in the illuminance by on-off switching control of artificial light are reported together with a proposal of artificial lighting control for constant brightness sensation. The sensation against the change in brightness can be interpreted by the frequency and the range of fluctuation of illuminance on the desk. The sudden change of task illuminance from higher to lower was found to be a decrease in brightness sensation of the desk. Estimated electric power consumption for lighting with the control of constant brightness sensation suggested a possibility of great reduction in power consumption compared to the case of continuous lighting.
