an aside on our eyes and relative colour
I wrote a HUGE post on digital camera white balance, and this is just a little excerpt on one of my favourite aspects of colour: how slippery it is!
So!
If you light a scene with a flame, say in a campfire or on a candle, you know it’s giving everything a warm glow, right? The way it’s doing that is: the light produced by the flame is itself made of mostly red and yellow wavelengths of light. It’s not producing any light on the blue wavelengths.
The way we, or a camera, perceive color is by coloured wavelengths being reflected off the object we’re looking at. The object doesn’t create the coloured light, it requires light of the right color to hit it for the colours of the object to be visible. Sunlight, white light, contains the full spectrum of colours, and so in bright sunlight the light itself shows us all the potential colours – which means it changes none of them, which means the light itself feels white.
When the flame on a candle produces light, it’s mostly producing red and yellow light, which means if it encounters a red object, it shows us the red, but if it encounters a green object, it can only show us the molecules inside that green color that are yellow, and the molecules inside that green that are blue don’t reflect any light. To our eyes, this tints the object yellowish in the candlelight.
However, if you stay a long time in a room lit only by candles, you probably feel like you can see green and blue and purple colours a little still. As I understand it (and my neurologist family members will I’m sure be haunted by this maybe oversimplified info so please follow the rabbit hole here if you’re curious, it’s really interesting stuff!) this is your brain compensating for the tinted information by shifting your identification of colours, maybe to try and help you discern as much information as possible from the limited visual data. You don’t stop knowing it’s warm light, but you adjust to it.
As an example, and here I’m talking about your eyes, remember, not the camera tech yet (we’ll get back to it shortly), here is a photo of a candle.
First off, let me assuage your dress-related paranoia – this is a teal candle.
To me, looking at the photo, this is clearly a teal candle. You can see it’s a lovely seafoam green at the top where it’s warmer and glowing through the melted wax, and a much more vibrant blue farther down, away from the flame.
So let’s take a closer look at these colours! I have isolated a few into bigger dots and overlaid them on the image where they were eyedroppered from:
And here are the same colours just on a neutral 50% grey background.
Here I have eyedroppered that brightest blue in the dots, the one on the bottom right of the image. This is how blue it is: not very blue! Pretty green still! Because that candle’s light cannot show us blue and purple wavelengths, we end up with an image where a cold green-grey starts to feel blue.
Our eyes work to compensate in limited-colour situations. We’re actually really good at it! And anyone who makes art commercially, anyone who designs colour for film and tv, advertising, fashion, games, etc? They all know this and use it when creating images. It’s why, given full colour vision, at a candlelit dinner, you can still tell your green veggies from your red ones.
And it’s not at all new! You can see this in Georges de La Tour’s famous candlelit paintings. The brightest light feels white, and colours still have some vibrance to them, and the scene feels rich, but, there’s no actual blues on the canvas, even though we have no trouble identifying the woman’s dress as light blue:
If you want to read more about how this applies to white balance settings on your cellphone or digital camera, the rest of the post is here:
