For the purposes of this chapter, terms used are defined as follows:
1. “After-hours lighting” means a reduction of standard light levels by 75% during the hours of 10:00 p.m. and 6:00 a.m. through the means of a control system or systems for outdoor general area lighting.
2. “Candlepower” means luminous intensity of a light in a specified direction measured in candelas (cd) (e.g., an ordinary wax candle has a candlepower of one candela).
3. “Cut off angle” (of a luminaire) means the angle, measured up from nadir, between the vertical axis and the first line of sight at which the light source is not visible, displayed as follows:
4. “Cutoff fixture” means a luminaire which has a light distribution where the candlepower does not exceed 2.5% of the lamps’ rated initial lumen output at an angle of 90 degrees above nadir, and does not exceed 10% of the lamps’ rated initial lumen output at a vertical angle of 80 degrees above nadir. This applies to all lateral angles around the luminaire.
5. “Luminous flux” means a quantitative expression of the brilliance of a source of visible light measured in lumens.
6. “Foot candle” (FC) means a unit of illumination when one lumen is evenly distributed on a one square foot area.
7. “Forward throw” means any downlight luminaire whose distribution pattern is Type IV (as defined by the IESNA). These luminaires have minimal backlight effect, thereby reducing light trespass.
8. “Full cutoff fixture” means a luminaire which has a light distribution where the candlepower does not exceed 0% of the lamps’ rated initial lumen output at an angle of 90 degrees above nadir, and does not exceed 10% of the lamps’ rated initial lumen output at a vertical angle of 80 degrees above nadir. This applies to all lateral angles around the luminaire.
9. “Glare” means the sensation produced by luminances within the visual field that are sufficiently greater than the luminance to which the eyes are adapted to cause annoyance, discomfort, or loss in visual performance and visibility.
10. “IESNA” means the Illuminating Engineering Society of North America.
11. “Illuminance” means lumens per unit area incident on a surface, measured in foot candles (1FC = 1 lm/sf).
12. “Illumination” is an alternative term for illuminance, most commonly used to avoid confusion between illuminance and luminance (e.g., it can be used in a qualitative sense to designate the act of illuminating or quantitatively by stating level of illumination).
13. “Light trespass” means light falling beyond the intended target area where it is not wanted or needed, including, by way of illustration but not necessarily limited to, across property boundaries.
14. “Lumen” (lm) means a unit of luminous flux (e.g., 1800 lumens is the approximate equivalent to a 100 watt incandescent bulb).
15. “Luminaire” means a complete lighting unit consisting of a lamp or lamps together with the components designed to distribute the light, such as reflectors, refractors, lenses, etc.
16. “Luminance” means the luminous intensity of a surface in a given direction per unit of projected area (e.g., candela/sf). This is not to be confused with ILLUMINANCE.
17. “Mounting height” means the vertical distance from the face of the luminaire to the surface area intended to be lit.
18. “Nadir” means the vertical line projecting downward to the ground from the center of the lens of a luminaire, displayed as follows:
19. “Standard light level” means maximum light level approved for the property.
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