Method for controlling the projection brightness of an image projected by an imaging device of a head-up display located in a motor vehicle, which image is reflected into the field of vision of a driver, whereby the driver perceives a virtual image, a brightness profile being determined for a background surface located behind the virtual image from the perspective of the driver, and a brightness control matrix being determined from the brightness profile, with the aid of which a projection brightness of the image projected by the imaging device is controlled, the following successive steps being carried out for a specific period of time: • recording several background images of the background surface using a camera characterized by the following further successive steps: • dividing each recorded background image into a predefined grid of sectors, the size of each sector comprising a plurality of pixels • determining a local brightness mean value over all pixels of each sector of a recorded background image • deriving a temporal brightness mean value of each sector for the period of time over all recorded background images • determining the brightness control matrix, consisting of the temporal brightness mean values assigned to the sectors • sector-individual control of the projection brightness for sectors (S') of the image projected by the imaging device depending on the brightness control matrix, the projected image being divided into a grid (R') of sectors (S') which corresponds to the grid of the recorded background image. • recording several background images of the background surface using a camera characterized by the following further successive steps: • dividing each recorded background image into a predefined grid of sectors, the size of each sector comprising a plurality of pixels • determining a local brightness mean value over all pixels of each sector of a recorded background image • deriving a temporal brightness mean value of each sector for the period of time over all recorded background images • determining the brightness control matrix, consisting of the temporal brightness mean values assigned to the sectors • sector-individual control of the projection brightness for sectors (S') of the image projected by the imaging device depending on the brightness control matrix, the projected image being divided into a grid (R') of sectors (S') which corresponds to the grid of the recorded background image. • dividing each recorded background image into a predefined grid of sectors, the size of each sector comprising a plurality of pixels • determining a local brightness mean value over all pixels of each sector of a recorded background image • deriving a temporal brightness mean value of each sector for the period of time over all recorded background images • determining the brightness control matrix, consisting of the temporal brightness mean values assigned to the sectors • sector-individual control of the projection brightness for sectors (S') of the image projected by the imaging device depending on the brightness control matrix, the projected image being divided into a grid (R') of sectors (S') which corresponds to the grid of the recorded background image.