A projection apparatus that projects an image on a screen based on input data including information on absolute luminance, the projection apparatus comprising: a peak luminance value acquisition unit configured to acquire a peak luminance value that is a luminance value on the screen when the projection apparatus is set to a predetermined state and when the projection apparatus projects an image on the screen at a maximum output gradation value, characterized by: a reference luminance value setting unit configured to set a reference luminance value to be higher than the peak luminance value using reference luminance information that indicates the relation between the reference luminance value and the peak luminance value, wherein the reference luminance value is reduced with a decrease in the peak luminance value; a reference relation information setting unit configured to set, based on the reference luminance value, reference relation information that indicates the relation between output gradation value and light output value, wherein the reference relation information setting unit is configured to set a curve representing the reference relation information with respect to the curve set in advance such that the upper limit value of the light output value of the curve representing the reference relation information is the reference luminance value; a relation information setting unit configured to set, based on the reference luminance value and the peak luminance value, relation information indicating a relation between an output gradation value and a light output value that is intensity of light for displaying an output image from the projection apparatus, wherein the relation information setting unit is configured to set a curve representing the relation information, by compressing the curve representing the reference relation information such that the upper limit value of the light output value is the peak luminance value LP, and such that the light output value is reduced at the same rate on all points; an output gradation value setting unit configured to set an output gradation value based on the input data and the relation information; and an output control unit configured to output an image based on the output gradation value generated by the output gradation value setting unit. a reference luminance value setting unit configured to set a reference luminance value to be higher than the peak luminance value using reference luminance information that indicates the relation between the reference luminance value and the peak luminance value, wherein the reference luminance value is reduced with a decrease in the peak luminance value; a reference relation information setting unit configured to set, based on the reference luminance value, reference relation information that indicates the relation between output gradation value and light output value, wherein the reference relation information setting unit is configured to set a curve representing the reference relation information with respect to the curve set in advance such that the upper limit value of the light output value of the curve representing the reference relation information is the reference luminance value; a relation information setting unit configured to set, based on the reference luminance value and the peak luminance value, relation information indicating a relation between an output gradation value and a light output value that is intensity of light for displaying an output image from the projection apparatus, wherein the relation information setting unit is configured to set a curve representing the relation information, by compressing the curve representing the reference relation information such that the upper limit value of the light output value is the peak luminance value LP, and such that the light output value is reduced at the same rate on all points; an output gradation value setting unit configured to set an output gradation value based on the input data and the relation information; and an output control unit configured to output an image based on the output gradation value generated by the output gradation value setting unit.