INTRODUCTION

The question that compelled me to write this article emerged after taking a closer look at the blue LED’s that pop up once in a while in our environment - during holidays, new year’s eve or just the occasional street signs. My night vision was simply having a hard time focusing on them, whereas red or yellow LED’s felt much more in focus.

WHAT IS LIGHT?

We can say with a great deal of accuracy that it is a real thing - from the moment it wakes us up, to our darkest, its absence takes away a fragile opening into collective reality. It is formally defined as a vibration in the electromagnetic field, with three important properties (among others): Wavelength, Energy and Frequency.

The wavelengths of vibrations can vary from being star-sized to competing with the slightness of atomic nuclei. Considering this, what we call visible light is only contained on a narrow section of this virtually infinite spectrum.

So narrow, in fact, that light can be seen when its wavelength is between ~750 and ~400 nm. 

COLOURS?

Different wavelengths between these limits will produce different colours in our mind’s eye ¹ , while what’s beyond will not be perceived visually - at least by our conscious selves.

Below you will find four different measuring results for the wavelengths of RED, ORANGE, YELLOW, GREEN, BLUE and VIOLET (always in that order). Since colours are an emergent property of our subjective perception, the exact wavelengths under which they appear will vary slightly.

There are exceptions: Claude Monet was (allegedly) lucky enough to see UV light - beyond the wavelength of Violet. ²

While looking at the world around you, your eyes will try and focus on an “average” colour - and usually that colour is not blue. 

If you consider the wavelength scale of colours, it’s green. Our eyes evolved to keep green in focus by default.

It makes sense to be most aware of variations in green, as it helps us navigate the natural world. It’s also a reason why artificial night-vision is in that colour. a

This compromise forces light towards the blue end of the spectrum to focus in front of the retina, while red light will focus in the back. Blue objects  will appear farther away (selective nearsightedness), while red is perceived as closer than it actually is.

So while both red and blue are “unfocused” by default, red brings a sense of immediacy and alertness — blue seems fuzzy and distant.

Interestingly, this diagram coincides with the refractive error of myopia (blue) and hyperopia (red). Green corresponds to normal vision. ⁷

Once the refracted light hits the retina, it’s over. No more light.

The retina covers a large area of the eyeball’s inside walls. It is made up of photoreceptors, each with their own function and specialisation. Whether they’re rods, cones, or ganglion cells, their job is to absorb photons and transform them into electrical signals, which are then carried onto the brain through the optic nerves - allowing us to see.

Rods are there to acquire information on the levels of luminosity, and make up most of our “resolution”. They outnumber cones by a factor of 20:1, even though cones are the only ones involved in signalling colour information to the brain. 

Cones also require 1000x brighter light ⁸ in order for us to begin distinguishing between different colours, and have been identified to respond either to Short, Medium or Long wavelengths — as such, we only see blue through the S-cones.

Rods are evenly distributed outside the central part of the retina, while their specialised counterparts are present mostly in the center — the fovea.

During daylight, there are a few factors that contribute to the blue bias:

No S-cones are present in the center, the place where most of the eye’s resolution comes from.

Blue receptors make up only 2–7% of the total colour receptors in our eyes. ⁹

Additionally, they have a third of the sensitivity of their counterparts. ¹⁰

This means that our eye’s focal point is mostly defined by colours in the red/green part of the visible spectrum, while our peripheral vision is mostly achromatic with “tints” of blue that do not add much to the overall spatial resolution.

Photopic vision ( day) and Mesopic/Scotopic vision ( night). If the cones are not receiving enough photons, only the highly sensitive rods will send information to the brain. Rods may have a sensitivity to light at around 500nm, which would make it between “blue” and “green”. ¹¹

So during the night blue seems to be favoured over the other colours, while light towards the red spectrum is hidden from our vision.

We are starting to understand more about what effects different colours have on our bodies and minds. This process is both scientific and cultural - as our knowledge about the world evolves, so does our perception of blue.

Culturally, we consider blue to be cool, relaxed, and soothing — although it is higher energy!

Multiple studies have shown that blue light increases alertness and can suppress the production of melatonin ¹², while surrounding yourself with red light will make it easier to fall asleep. ¹³ This is counter-intuitive, but it is now common knowledge among those who work in front of a screen that blue light makes it harder to relax and have a restful sleep — it is basically telling our bodies that is it daytime all the time!

For example, the American Medical Association put out a press release that compares between the different colours of street lights:

Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity. ¹⁴

Typically, office building lighting is designed with a colour temperature of 4000k, which is “cool, blue light”, but a bright sunny day can go up to around 30.000k. So why is it not causing terrifying levels of anxiety?

Lighting scientist Ian Ashdown writes about the misconstructed notion of “blue light bad”: 

Reading the papers of course provides more information. Dawson et al. (2001) sacrificed five rhesus monkeys after exposing them to between 5 and 54 joules/cm2 of blue light from a 458 nm argon laser. This is roughly equivalent to staring at the noonday sun without blinking for 3 to 25 minutes. ¹⁵

Daylight, yet still scarily blue, remains the gold standard, and we cannot fully mimic it through artificial lighting. Commercially viable blue LED’s have only been around since the mid 90’s — and their invention was so important, it was celebrated with a Nobel prize. ¹⁶

As we find more uses for blue light, we begin to understand our responses to it, and so far the results have been somewhat contradictory.

Short wavelengths are acknowledged as providing enhanced peripheral vision at the low levels of illuminance typically associated with street lighting. ¹⁷

They also are harmful to nocturnal wildlife, both through their intensity and widespread use. ¹⁸

Credit: Radio New Zealand

According to the Purkinje effect, which we have discussed previously, the human eyes are much more sensitive to blue frequencies during the night. White LED’s used in headlights (also: Xenon lights) are particularly damaging to our sight and can even blind and kill motorists.

Why? The mechanism under which white light is emitted is actually a combination between high intensity Blue and Yellow frequencies. ¹⁹

Credit: Philips Automotive

Recent technologies involving high frequency visible light have been used to kill harmful bacteria in the hospital environment (such as Staphylococcus aureus and Clostridium difficile), while being harmless to pacients and staff.

It seems to be a much safer option than previously used UV-light and can provide continuous treatment of air and surfaces. ²⁰

Credit: University of Strathclyde

Blue light makes it difficult to see veins and thus may be used to discourage drug use, ²¹ although it may also increase drug use-related harm. ²²

Credit: AP Photo/Michael Rubinkam

Borrowing a trick used in the steel and glass manufacturing industries, researchers have found that commercially available blue light can make it easy to contend the red light emitted by hot objects (in this case, engulfed by unwanted flames).

This way they can see through fires and assess the damage that was inflicted. ²³

Credit: National Fire Research Laboratory/NIST

Architects and designers are already taking advantage of the relatively cheap blue light.

For example, the Wellcome wing of the Science Museum in London is based on the principle that blue light leaves more to your imagination and may even be “slightly discomforting”. ²⁴

Credit: MJP Architects

Of course, there will be lots of art using blue light as the main conceptual pillar, like this ²⁵ installation at London’s Victoria Miro gallery.

Whereas the previous examples need to base their evolution in real-life, testable, falsifiable and sustainable movements, art can expand on the subjective nature of light and how it relates to our less conscious selves.

Credit: Victoria Miro / Doug Aitken