Light Distribution Curves
Light distribution curves provide information about the way light is distributed from the fixture and also how that light falls upon a surface. The candlepower distribution of a luminaire depends upon reflector design, shielding type, and lamp-ballast selection.
There are three types of the curves:
Polar luminous intensity curve: Polar curve is defined as a graph representing the light distribution of a lamp (luminous intensity) in a horizontal or vertical plane. The curve shown provides a visual guide to the type of distribution expected from the luminaire e.g. wide, narrow, direct, indirect etc. in addition to intensity.
Cartesian luminous intensity curve: The diagram indicates the distribution of luminous intensity, in candelas of the luminaire. The curve shown provides a visual guide to the type of distribution expected from the luminaire e.g. narrow or wide beam etc, in addition to intensity . This diagram is useful when light intensity changes rapidly within a small angular area.
Illuminance cone curve: Usually used for spotlights or lamps with reflectors, the diagram indicates the maximum illuminance at different distances away from the lamp.