A control apparatus includes a calculator that calculates a target dimming rate of a projection display apparatus based on a feature quantity of image data, a diaphragm controller that controls a diaphragm position of a diaphragm based on a target diaphragm position set for each range to which the target dimming rate belongs, and a light source controller that controls a light quantity of a light source on the basis of the target dimming rate and the diaphragm position.