1. A method for converting an original image sequence whose luminance values belong to a given dynamic range, said method comprising: converting, image-by-image, the dynamic range of the luminance component of each image of the original image sequence by applying a dynamic range conversion operator to the luminance component of each image of the original image sequence to obtain a modified luminance component whose values belong to a lower dynamic range than that of the original image sequence, wherein it also comprises: correcting the dynamic range of the values of the luminance component thus modified by reducing it by a value calculated from a global characteristic of the original image sequence.