An image processing apparatus includes a luminance value calculation unit configured to calculate a luminance average value and a luminance peak value from an image obtained by image-capturing for each of frames formed by dividing one screen, a first calculation unit configured to combine the luminance average value and the luminance peak value obtained for each of the frames, a second calculation unit configured to calculate an average value of composite values equal to or more than a predetermined threshold value among composite values obtained by the first calculation unit, and a setting unit configured to set knee strength based on the average value of the composite values obtained by the second calculation unit.