Method for controlling the projection brightness (PH) of an image projected by an imaging device of a head-up display located in a motor vehicle (K), which image is reflected into the field of vision of a driver (F), whereby the driver (F) perceives a virtual image , a brightness profile being determined for a background surface (A) located behind the virtual image from the perspective of the driver (F), and a brightness control matrix being determined from the brightness profile, with the aid of which a projection brightness (PH) of the image projected by the imaging device is controlled, the following successive steps being carried out for a specific period of time (T): • recording several background images of the background surface (A) using a camera characterized by the following further successive steps: • dividing each recorded background image into a predefined grid (R) of sectors (S), the size of each sector (S) comprising a plurality of pixels (P) • determining a local brightness mean value (HM1) over all pixels (P) of each sector (S) of a recorded background image • deriving a temporal brightness mean value (HM2) of each sector (S) for the period of time (T) over all recorded background images • determining the brightness control matrix , consisting of the temporal brightness mean values (HM2) assigned to the sectors (S) • sector-individual control of the projection brightness (PH) 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 (R) of the recorded background image . • recording several background images of the background surface (A) using a camera characterized by the following further successive steps: • dividing each recorded background image into a predefined grid (R) of sectors (S), the size of each sector (S) comprising a plurality of pixels (P) • determining a local brightness mean value (HM1) over all pixels (P) of each sector (S) of a recorded background image • deriving a temporal brightness mean value (HM2) of each sector (S) for the period of time (T) over all recorded background images • determining the brightness control matrix , consisting of the temporal brightness mean values (HM2) assigned to the sectors (S) • sector-individual control of the projection brightness (PH) 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 (R) of the recorded background image . • dividing each recorded background image into a predefined grid (R) of sectors (S), the size of each sector (S) comprising a plurality of pixels (P) • determining a local brightness mean value (HM1) over all pixels (P) of each sector (S) of a recorded background image • deriving a temporal brightness mean value (HM2) of each sector (S) for the period of time (T) over all recorded background images • determining the brightness control matrix , consisting of the temporal brightness mean values (HM2) assigned to the sectors (S) • sector-individual control of the projection brightness (PH) 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 (R) of the recorded background image . <EOS>