1. A method of operating a display comprising: providing a display; acquiring an image of a structure by measuring, for each of a plurality of elements of the image of the structure, a magnitude representing an element of the structure; providing a plurality of contrast setting control buttons comprising a first contrast setting button that directly and independently modifies dark parts of the image of the structure and a second contrast setting button that directly and independently modifies light parts of the image of the structure; digitizing the magnitude of each of said plurality of elements according to a direct mode by assigning to each of said plurality of elements a digitized value d representing the measured magnitude of each of said plurality of elements; displaying a direct image on the display by assigning to each of said plurality of elements a luminosity l corresponding to the digitized value d of each of said plurality of elements and transmitting to the display the luminosity l of each of said plurality of elements; transforming the direct image to a transformed image by assigning to each of said plurality of elements a digital value i which corresponds to the digitized value d of each of said plurality of elements; and displaying the transformed image on the display by assigning to each of said plurality of elements a luminosity m corresponding to the digital value i of each of said wherein the digital value d of each of said plurality of elements is converted into the digital value i of each of said plurality of elements according to a reversal function f, said reversal function f having a slope -b for zero values of d and a slope -1/a for maximum values of d, to transform the darkest and the most luminous parts of the direct image, and whereby the plurality of contrast setting control buttons act directly on slope -b and slope -1/a and the reversal function f is determined on the basis of slope -b and slope -1/a.