Luminous intensity distribution curves are typically represented in polar plots because this format allows us to visualize both the orientation and the light distribution of the light fixture. The candlepower distribution of a light fixture depends upon reflector design, shielding type, and lamp-ballast selection. It is assumed that the light fixture position is at the crossing of two axes (horizontal and vertical), and that 0° (nadir) is beneath the light fixture. Other angles, which represent the various placements of a photocell as it moves in a circular pattern around the light fixture, are marked on the graph as well.