Outdoor lighting and light pollution: why warmer tones are chosen

A glowing night sky, light spilling into a neighbour’s window and effects on wildlife are all forms of light pollution. Why warmer tones are chosen for outdoor lighting.

Many city dwellers only see a starry sky once they leave town. The reason is not just air quality but night-time light itself: part of the light from streets, yards, advertising and buildings spreads into the sky and turns it into a grey-orange dome. This is called light pollution. It cannot be eliminated entirely, but the way every outdoor light is chosen, from a house yard to a street, makes a difference.

Three forms of light pollution

Light pollution shows up in several ways:

• skyglow: light spreading upwards and towards the horizon, scattering in the atmosphere and brightening the night sky;
• light trespass: light falling where it is not wanted, such as a neighbour's bedroom window;
• glare: excessively bright, exposed sources that dazzle drivers and pedestrians and reduce their ability to see.

All three affect both comfort and safety. Contrary to expectations, glaring light weakens night vision.

Why blue light causes more trouble

How much light scatters in the atmosphere depends on wavelength: short-wavelength blue light scatters far more than long-wavelength red-orange light. That is why the daytime sky looks blue. At night the same physics applies to artificial light: cool white light with a strong blue component scatters more in the atmosphere and contributes more to skyglow.

In addition, many nocturnal animals and insects are sensitive to blue light. Cool light has a stronger effect on their behaviour: feeding, migration and breeding. For people too, blue light in the evening and at night affects the biological rhythm more.

For these reasons, organisations that work to protect the night sky recommend a colour temperature of 3000K or lower for outdoor lighting. Near some nature areas and observatories, even warmer, amber-toned light is preferred.

Colour is not the only answer

Choosing warm-coloured lamps is an important step, but direction and quantity of light play a bigger role. Poorly aimed warm light can pollute more than well-aimed cool light. The key principles are:

• light should go only where it is needed, downwards; open globes and decorative “ball” lights that shine above the horizon cause the most problems;
• choose shielded fittings that concentrate light downwards;
• brightness should match the task, since you do not need stadium lighting to see a garden path;
• light should be on only when needed, and timers, photocells and motion sensors automate this.

Practical advice for home yards and country houses

• Choose 2700–3000K lamps for door and path lights; near gardens and nature, warmer amber tones suit too.
• Make sure wall-mounted fittings aim light downwards and the lamp is not visible from outside.
• Turn lights that face a neighbour's yard or windows in another direction.
• Install motion-sensor lighting instead of lights left on all night.
• If you want to uplight trees or a façade, use a narrow beam aimed only at the object and switch it off after midnight.

These measures also save energy, because light spilled where it is not needed is electricity wasted.

A misconception about safety

People often say “the more light, the safer”. In reality, harsh bright light deepens shadows and causes glare: the area behind a bright floodlight becomes even harder to see. Evenly distributed, glare-free, moderate light provides better visibility. A light that suddenly switches on via a motion sensor also draws more attention.

Commercial and public premises

The same principles apply to shops, car parks and advertising: warm or neutral-warm tones, downward light and lower brightness late at night. Switching off or dimming advertising and window lighting after business hours benefits both neighbours' comfort and electricity use.

Zaferoğlu Elektrik's range is not limited to home bulbs; it also includes high-power LED lamps for outdoor and industrial use. For yard or street lighting, favouring 3000K or warmer protects both the night sky and the neighbours.