NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 14 Different types of lighting may influence how an object and its features are seen within a specific setting or from various distances. The direction of the light may influence what can be seen by illuminating a narrow or wide expanse of an object Color of Light All light has color, containing primary colors within the color spectrum. Primary colors of light are red, green, and blue. Primary colors of light should not be confused with the primary colors of pigments, which are red, yellow, and blue. The three primary colors of light can combine to produce any other color, including white. The secondary colors of light are formed when any two primary colors combine. The three secondary colors are magenta (red and blue), yellow (red and green), and cyan (blue and green). The human eye is more sensitive to yellowgreen gradients of the visual spectrum (about 550 nanometers) than it is to red or blue at the ends of the spectrum. The appearance of color from a light bulb is commonly described using the Kelvin (K) temperature scale. The color of the glow/light emitted at different temperatures are the basis for the standard Kelvin color temperature scale. Colors at lower temperatures are warmer (red, orange, yellow); white is a midrange temperature; and colors at higher temperatures are cool (blues, violet, ultraviolet) (NIST 2021). Studies show that artificial light at higher color temperatures (> 3,000 K) interferes with normal biological rhythms (Lin et al. 2019). 3.1.2 Types of Light Pollution There are different types of light pollution, and each type is associated with different effects: • Glare: Excessive brightness that causes visual discomfort or visual impairment. • Skyglow: Overall brightening of the night sky caused by atmospheric reflection of outdoor lighting and other causes. • Light trespass: Light falling where it is not intended or needed. • Light clutter: Bright, confusing, and excessive groupings of light sources. • Over-illumination: Lighting intensity higher than that which is appropriate for a specific activity. Lighting Design Lab Color temperature scale. Visual description of glare, light trespass, and skyglow. 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 Candlelight Tungsten Light Early Sunrise Household Light Bulbs Electronic Flash Noon Daylight Direct Sun Overcast Daylight Blue Sky
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