Light and Perspective
I’m sure I’m not the only woman who’s found herself one minute sat in the hairdresser’s chair admiring her new hair colour and the next minute sat in her car looking in the mirror wondering how her hair managed to do a chameleon-like shift from blonde to red in the short time it took to walk across the street!
As I’ll keep saying throughout this blog, I don’t hold any of my lovely hairdressers responsible! All of them would explain, in a much better fashion than me, it’s not just the mix of the chemicals that has an impact, it’s the molecular structure of your hair and — most importantly — the source of the light that’s hitting your head. It’s actually quite fascinating, the physics behind our hair colour…
It was Isaac Newton, way back in the 1600’s, who first realised that colour isn’t an integral part of things — so the colour of your hair isn’t ‘in’ your hair (I don’t think Newton did any experiments on hair, but it’s all relative…). What he discovered was that light is made up of a spectrum of different colours and the colour we perceive an object (or our hair) to be is wholly dependent on which of the colours are reflected back by the object (or our hair’s) surface.
Light’s a form of electromagnetic radiation made up of different wavelengths, and it’s these different wavelengths that correspond to light’s spectrum of colours. Natural sunlight contains the full spectrum, so in daylight a full rainbow of colours is available for reflection or absorption. I guess this means that under the sun’s the place to be to see the ‘truest’ picture of my actual hair colour!
(Sidenote, I feel like there’s something glorious in the fact that natural light is made up of a spectrum of colours, but when they’re all joined together they look pure white — just like our hair when the pigment cells die).
Of course, the composition of our hair — the configuration of the molecules that make up our strands of hair — has a role to play too, having an impact on which wavelengths of light are absorbed and reflected. Otherwise we’d all have the same colour of natural hair, no matter what source of light we were standing under!
The colour rendering index (CRI) is something that’s sometimes used to signify the purity of a light source in comparison with natural light, for example in different types of light bulbs. Basically, the closer an artificial light is to natural light, the higher the CRI. So, it’ll come as no surprise that fluorescent lights have a pretty low CRI! We should really just avert our eyes from the mirrors when we’re in a shop with fluorescent lights — that yellow skin tone and freaky looking hair colour we see reflected back are really just figments of a fluorescent abomination…
There’s obviously a lot more to it than this very brief foray into a wee bit of physics, but hopefully I’ve helped answer some of the questions as to why our hair can look so many different colours and shades, even on the same day — as the two photographs above demonstrate… they were taken within minutes of each other, the first inside in artificial light and the second outside in natural daylight.
And, since we now know that natural light produces the most accurate representation of something’s ‘true’ colour I think it’s fair to say that I’m well on my way to going grey…
