A calculated measure of the brightness value of a pair of binoculars. The higher the luminous intensity, the better the binoculars are suitable for twilight situations. The formula for calculation is: Divide the lens diameters by the magnification. Square the result. Relative luminous intensity: While the geometric luminous intensity only takes into account the objective diameter and the magnification, the relative luminous intensity describes the additional increase in performance due to special types of coating and, compared to an uncoated glass, is expressed as a percentage increase (e.g. 60%).