What is Cutoff Distribution
Cutoff distribution, in the context of the lighting industry, refers to a classification system that regulates the light distribution from a luminaire. It is designed to control the amount of glare produced by a luminaire, particularly at specific vertical angles, in order to enhance the comfort and safety of drivers. The cutoff distribution classification system categorizes luminaires based on the intensity of light emitted at certain vertical angles. There are different categories within this classification, each with specific criteria for intensity limitation.
The first category is the Non-Cutoff distribution, which refers to a luminaire light distribution without any intensity limitation. In other words, there are no restrictions on the amount of light emitted at any vertical angle.
The second category is the Semi-Cutoff distribution, where the intensity of light does not exceed 20% of the rated light at 80 degrees vertical angle from above nadir. Additionally, the intensity must not exceed 5% of the rated light lumens at 90 degrees from nadir. This limitation applies to all lateral angles around the luminaire.
The third category is the Cutoff distribution, where the intensity of light does not exceed 2.5% at or above 90 degrees of the rated lamp lumens from nadir. Additionally, the intensity must be less than 10% of the rated light lumens at 80 degrees vertical angle above nadir.
The fourth and most restrictive category is the Full Cutoff distribution, where the intensity of light is zero above 90 degrees from nadir. This means that the light emitted by the luminaire will only hit the ground below. Additionally, the intensity must not exceed 10% of the rated light lumens at or above 80 degrees. Similar to the semi-cutoff classification, this limitation applies to all lateral angles around the luminaire.
By implementing the cutoff distribution classification, the lighting industry aims to minimize glare and light pollution by directing the light downward and preventing excessive light emission at specific angles. This helps to create a more comfortable and safer lighting environment, particularly for drivers on roadways.