If the distribution of the light is symmetrical in all directions around a vertical line, as with most recessed incandescent downlights, then only one candela distribution curve is necessary. In fact, only one half of that curve is usually shown, with the missing half implied to be an exact match. This is done primarily to simplify the reporting. If, however, the distribution of light is not symmetrical in all directions around a vertical line, candela values will be taken in more than one vertical plane through the light fixture but are shown in the same plot as in the illustration below. Only half of the curve for each plane is shown if the candela distribution is symmetrical within the plane