And at C is 0° -180°, it makes the term of I (cd) varied in the trend of C angle. Moreover, the maximum luminous intensity (Imax) is different too.The polar curve or isocandela can plot by usingPhotometric Toolbox program. It uses the information from the experiment that shown in the IES file. The polar curve is depend on the luminair which reflect the light in the way. The beam angle can get from the angle of 50% of I max. It will be the beam angle of the gramma