I was on a bus recently and happened to be people watching – as is very usual for me in any circumstance. Anyhow, I was gazing covertly at a girl from her reflection in the bus window when I realised how strange the actual reflected image was.

On reflection…

I realised that I was only seeing the brightest parts of the whole reflected image; the hair which was light blonde was almost opaque, whereas in the shadows of the face I could see almost no reflection and therefore was able to see the outside world beyond the window. It’s a completely natural phenomena but trying to understand what was happening mystified me for a couple of minutes, and then it hit me!

↓ below : see how the dark fur of the cat in the reflection allows us to see the view through the window but the white parts block our view

cat reflection example

What we see

If you haven’t worked it out, you need to go back to thinking about exactly what we see when we are looking at stuff. We only see things because the light in the room (or the light outside) is bouncing off that stuff and hitting us smack bang in the eyes. So when I look at my other halfs red jumper, I see it because light has hit the jumper and bounced right into my eyes. Now for the relevant bit… The reason I see that it’s red is because the rest of the light spectrum – the orange, yellow, green, blue, indigo and violet – is being absorbed, or soaking in to the jumper, and hence it’s only the red light in the spectrum that’s being reflected back at my eyes. It’s the same for the other component colours of course (orange, yellow, green etc) and colours that aren’t obviously in the spectrum are made from combinations of colours (cyan = blue + green, brown = part red and part yellow etc).

When we see white or very bright object, the whole or most of the whole spectrum of colours are being reflected back at us.

Incidentally this Additive Colour effect is just how colours work in computing where you add colours together to get brighter variants, as opposed to in paint  (Subtractive Colours) – where colours are mixed to darken the tones.

Black is the new nothing

In a strange opposition to the rule, when we see a black object we are seeing a lack of reflected light. In fact when we are looking at a really black object, we are in effect seeing literally nothing, a void of little-to-no light information, which reveals the answer to the original conundrum. The reflection on the bus window is showing us only the reflected light, so the light parts of the reflection are present, the brightest colours even block out the view, but in the dark areas and blacks there is nothing, as if that part of the person or thing that’s being reflected isn’t even there – which is really just how our eyes always witness them.

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