An image processing apparatus comprising: an image acquisition unit adapted to acquire a hybrid log-gamma HLG HDR image signal which is normalized at a luminance level of the reference white and to generate a linear image signal by applying an inverse function (OETF -1) of an opto-electric transfer function OETF for the HLG scheme to the acquired input image signal, a transformation unit configured to transform the linearized image signal output by the image acquisition unit based on a scheme which maintains a display luminance level of the reference white unchanged; a control unit adapted to control operations of the image acquisition unit and the transformation unit and to determine the peak luminance (Lp) of a display; wherein in order to maintain a display luminance level of the reference white unchanged, the transformation unit is configured to: - execute a linear transformation on the image signal output by the image acquisition unit using a gain value, and - execute a gamma transformation on the image signal subjected to the linear transformation using a gamma value chosen so that the display luminance level of the reference white is restored to its original luminance level, wherein the transformation unit is configured to calculate the gain from the peak luminance level (Lp) of the display and an upper limit of the luminance dynamic range of the image signals such that the maximum luminance level expressible by the display signals can be aligned with the peak luminance level of the display. an image acquisition unit adapted to acquire a hybrid log-gamma HLG HDR image signal which is normalized at a luminance level of the reference white and to generate a linear image signal by applying an inverse function (OETF -1) of an opto-electric transfer function OETF for the HLG scheme to the acquired input image signal, a transformation unit configured to transform the linearized image signal output by the image acquisition unit based on a scheme which maintains a display luminance level of the reference white unchanged; a control unit adapted to control operations of the image acquisition unit and the transformation unit and to determine the peak luminance (Lp) of a display; wherein in order to maintain a display luminance level of the reference white unchanged, the transformation unit is configured to: - execute a linear transformation on the image signal output by the image acquisition unit using a gain value, and - execute a gamma transformation on the image signal subjected to the linear transformation using a gamma value chosen so that the display luminance level of the reference white is restored to its original luminance level, wherein the transformation unit is configured to calculate the gain from the peak luminance level (Lp) of the display and an upper limit of the luminance dynamic range of the image signals such that the maximum luminance level expressible by the display signals can be aligned with the peak luminance level of the display. - execute a linear transformation on the image signal output by the image acquisition unit using a gain value, and - execute a gamma transformation on the image signal subjected to the linear transformation using a gamma value chosen so that the display luminance level of the reference white is restored to its original luminance level, wherein the transformation unit is configured to calculate the gain from the peak luminance level (Lp) of the display and an upper limit of the luminance dynamic range of the image signals such that the maximum luminance level expressible by the display signals can be aligned with the peak luminance level of the display.