Lighting in Design Q2 2024

What is light pollution?

Why have LEDs become a massive contributor to this phenomenon – Otto Horlacher from Giantlight investigates… L ight pollution is defined as ‘human made altera tions of outdoor light levels from those occurring naturally’. “To better understand this phenom team reduced the light level on the client’s desk to less than 300 lux. Different sources & their light

enon – let’s first look at how humans see light,” says Otto Horlacher. “The human eye can see visible light – in the spectrum range from about 380nm (almost ultraviolet) to just past 700nm (near infra-red).” Humans have two main photoreceptors in the retinas of our eyes: Rods and Cones. We have three ranges of vision: • Photopic vision engages our cone receptors and is used in daylight conditions when there is sufficient light (as low as 10cdm 2 and upwards). Cones comprise red, green and blue receptors – humans have about 6 million cones and more than 100 million rods. • Mesopic vision is when neither cone nor rod are fully engaged – this occurs in twilight conditions. • Scotopic vision is when the rods engage and are used in night-time conditions. Typically, we cannot see colours at night because the cones are not engaged. “Our eyes are incredibly sensitive to light,” says Horlacher. “On one occasion, I was called into the dealer principal’s office at a high-end car dealership as he was complaining that the lights were giving him a headache. I could immediately tell that his office was over-illuminated, and he was receiving about 800lux on his table workspace. His pupils were contracting to adapt to the high light level, and he would then focus on his computer monitor that was at less than 200nits, forcing his pupils to expand. Naturally he was going to get sore and tired eyes.” To solve the problem, the

To further understand the effect of light pollution, we need to quickly delve into different light sources and what they produce. “The critical aspect here is to look at the size of the light source in relation to the amount of light it produces,” explains the illumination expert. “Incandescent (old-style globes) see a tungsten wire positioned in a near vacuum. Electrical energy is run through the filament making it burn ‘white hot’ – typically a filament would be 3cm long and 1mm in diameter, which translates to 30mm x 1mm producing about 1 300 lumens for a 100W. So that means 1 300 lumens divided by the area of the light source 30mm = 43 lumens per mm 2 .” Fluorescent lights (either hot or cold cathode), are gas-filled tubes of normally argon or mercury vapour, with electrodes at either end. “When an electrical pulse (starter device) is sent through the gas from one electrode to the other, the electrons in the gas are repositioned to face in one direction,” explains Horlacher. “This allows an electrical current to flow through the gas, which is then energised and emits ultraviolet energy. This energy meets a phosphorous coating on the inside of the glass (the white powdery substance) which converts the ultraviolet energy into white light.” A 36W tube, 1 200mm x 26mm, will produce 3 200 lumens – 3 200 lumens divided by the area of the fluorescent tube = 48 984mm 2 or less than 0.067 lumens per mm 2 . The third is gas discharge. “Let’s use a metal halide 150W lamp that operates similarly to a fluorescent bulb in that it has two

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LiD Q2 - 2024