What's the difference between warm and cool light?

02 December 2021

Author: Kate Green

christmas lights cool light warm light

How does warm light differ to cool light?


If you haven’t already put up your Christmas decorations, then this weekend is likely to be the occasion for it. The majority of the nation agree that the first weekend of December is the perfect time to begin stringing gorgeous lights up outside your house and wrapping the Christmas tree in tinsel. If you’re in the market for some new decorative lights, you’ll need to decide between multi-coloured or white lights. And if you’re considering white lights, the next question is whether you opt for cool white or warm white. So many decisions to be made!


Cool white lights have more of a blue-ish tinge to them and work particularly well if you’re opting for an icy, snowy theme. Warm white lights appear more yellow or golden in colour and compliment a red and gold theme particularly well. Warm light and cool light have different effects on your eyes which we’re going to delve into on the blog today.


Aside from colour, the main way in which warm and cool light differ is their Kelvin value. ‘Light temperature’ is measured in Kelvins which provides an indication to the type of white glow they give off. Warm light is between 2,700-3,200 Kelvins, while cool light is between 5,000-6,000 Kelvins. In between warm and cool light sits daylight at 4,000-4,500 Kelvins.


Which areas have warm light and which have cool light?


Warm light tends to be used in more cosy spaces throughout the home, such as living rooms or bedrooms. Warm light is easy on the eyes helps you to wind down, while cool light is more suitable for brighter, focused areas such as the kitchen or bathroom. Cool light also tends to be used in commercial and office buildings as it is more appropriate for a work environment. Some people may choose to use bulbs which mimic daylight throughout their home, but it really does just come down to personal preference.


How can cool light and blue light affect your eyes?


As we look into the effects of different types of light with reference to your Christmas tree decorations, we should also touch on LED lights as these are what most Christmas lights are. Unlike other types of light, LEDs don’t emit a constant stream of light. They actually flash constantly but the flashes happen so quickly that our brains don’t notice it. Because the human eye has such fast movement, we can actually see over 2,000 flashes of light per second. Even if we don’t realise that this flashing is happening, it can have the effect of causing eye strain, which is why LED lights sometimes get a bad reputation of being harmful to your vision.


Some studies have shown that LED lights can emit UV rays and it is also known that cool white lights emit more UV radiation than warm white lights. Further to this, a 2011 study in the American Journal of Public Health revealed that there was a 12% increase in eye diseases when the person affected had been exposed to more cool fluorescent lights. Cool white light and blue light (emitted by digital devices such as smartphones and tablets, as well as some LEDs) have shorter wavelength light sources. Sunlight also has a short wavelength, meaning that these types of light can be more damaging to your eye health.


Too much exposure to UV rays can bring on cataracts and AMD (age-related macular degeneration). Of course, this is mainly dependent on how much time you spend around sunlight, blue light from digital devices (which is a form of cool light), and cool white lighting in the home or workplace. We all know that staring at the sun causes permanent retinal damage in just a few minutes, but this happens on a smaller scale and at a much lower level with cool white LED lighting. Your risk of visual damage caused by light exposure is even greater if you have light coloured eyes, namely blue or green, as they let in more light, and therefore more UV damage.


How can you protect your eye health from bright lights?


To protect your eyes from UV rays, the best thing you can do is wear UV radiation blocking sunglasses. In the UK and Europe, standards on sunglasses sold are really strict. To meet guidelines, all manufacturers must ensure that their lenses block between 99 and 100% of UV radiation. This prevents almost all UV rays from reaching your eyes and causing eye conditions such as cataracts and AMD.


While sunglasses are great for protecting your eyes whilst you’re outside, some things you can do inside the home include:

  • Turning off the lights where possible and relying on natural daylight
  • Use warm white light in places that you’re reading (as it is more comfortable
  • Avoid digital screens in dark rooms as focusing on these can strain your eyes
  • Set your screens’ brightness to dimmer than the room’s lighting around you
  • Set your screen to warm lighting (it may appear slightly yellow- or orange-toned) as opposed to the bright blue-toned standard cool lighting. Blue light has a shorter wavelength, leading to more eye strain.


Above all, remember to regularly attend eye tests in order to detect any damage from lights, which may affect your vision long-term. Blue light and cool white light are worse for your eyes so, if you spend a lot of time in environments lit by them, or working with blue light screens, then having your eyes checked is even more important.

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