Color temperature is the temperature at which a black body emits radiation matching a light source's spectrum. Higher color temperatures have more blue, lower have more red. Described as cool or warm shades, humans adapt to sunlight's spectrum. LEDs with higher color temperatures are cheaper but may disrupt biorhythms. Turnable White fixtures allow adjustment of light shade, offering flexibility for various environments and mimicking natural light changes.
Vision is formed by analyzing rods and cones in our eyes. Rods detect black-and-white, while cones perceive color. RGB LED lights mix red, green, and blue to create colors and are used in displays and lighting. White light from RGB LEDs can be inconsistent, so blue-based LEDs with phosphor are used for pure white. RGBW LEDs, combining white, are used for residential lighting. Specialized systems can use more colors.
Color rendering assesses how accurately colors appear under different light sources. CRI, used since 1965, rates fidelity on a scale up to 100 but ignores color vividness. The newer IES TM-30-20 standard evaluates both fidelity (Rf) and gamut (Rg) using 99 color samples, offering improved precision for selecting LED lighting in varied environments like retail, offices, and museums.
Dimming reduces LED light output using linear or PWM methods. The linear method lowers current, avoiding electromagnetic interference, making it suitable for medical or research settings, but may reduce efficiency and requires fixture adjustments. PWM uses constant current pulses with variable width to control brightness without flicker. TRIAC dimmers, designed for incandescent lamps, need compatible LED drivers.
The optical system in LED fixtures creates the required light distribution using components like lenses, reflectors, and diffusers. Beam angle defines distribution type, distinguishing spotlights from general fixtures. Diffusers vary by light transmission and uniformity. Materials for optical elements include PMMA, silicone, aluminum, tempered glass, polycarbonate, and ABS, supporting 3D printing.
