An all white area has an average intensity of 1 and an all black area has an average intensity of 0.
You can calibrate intensity measurement by right-clicking on a defined circle, area or rectangle and select Set Average Intensity in the popup menu. Next you can indicate if the selected area corresponds with a white or black area. See Set intensity.
*Only the parameters selected in the Measurements List Columns options box are displayed in the Measurements list window.