|Let you set the darkest and lightest pixel in the input image to be mapped to the luminance scale of the display device. Two vertical markers on the histogram indicate the lower and upper limit of the intensity levels. All pixels whose value is equal or lower than the lower limit will be displayed in black. All pixels whose value is equal or higher than the upper limit will be displayed in white. You can change the lower or upper level by dragging a corresponding marker with the cursor, or you can move the window they form by placing the cursor between the markers. You can also indicate the desirid values of the levels in the respective boxes.