Okay, I'm just going to address the elephant in the room as I start,
yep, we are three months into Britain's third lockdown at the minute,
uh, I desperately need a haircut, and there is a sideways wind here, so
we're just going to have to deal with what's going on up here.
According to the manufacturer, my hoodie is grey.
That was what I bought.
I picked the most generic colour possible.
It's not going to clash with anything I film against,
it's not going to blend into a green screen or a blue screen.
Although to be fair, if I am filming under a blank grey sky,
it can make the shot look a little dull.
But if I am filming against a grey sky,
and we compare the colours between the clouds and my hoodie...
then this looks just a little bit blue. Or maybe purple?
It looks a bit different in all those thumbnails.
I mean, technically those aren't all the same hoodie,
I've got several, but they're all identical.
To explain the magical colour-changing hoodie,
we need to talk about how colour perception works,
and also about the history of laundry.
First up: a brief run through what you probably already know from school.
Electromagnetic radiation is a spectrum,
that includes x-rays and microwaves and radio waves and visible light.
The difference between those types of radiation is the wavelength.
We have special cells called "cones" in the back of our eyes, three types of them,
and each type reacts to a small set of different wavelengths.
Which are, oh-so-conveniently,
the wavelengths that the atmosphere easily lets through.
The wavelengths for each type of cone overlap a bit, it's not precise,
but it's roughly equivalent to red, green and blue.
So if these cells notice radiation but these mostly don't, you see blue.
If these and these do, but these don't? Magenta.
And if all of them do, at just the right balance?
Well, that'll be white, or grey.
But you have to remember that colour is not a real thing.
colours are experiences, the philosophical term is qualia,
your brain just creates colour in your head
based on the signals it receives from those cells.
Depending on the context,
you can see the exact same wavelengths as different colours, even at the same time.
There are a lot of optical illusions that play with that.
colour perception isn't just about wavelengths,
it's about comparing those wavelengths to everything around.
A camera doesn't do that,
as I shall now demonstrate with a white wall.
It's daytime as I record this,
and the camera is set up for the daytime light that's shining in.
Bright sunshine.
Now, there is an official, precise definition of "average sunlight",
it's called Illuminant D65,
it's meant to simulate the middle of the day in Western Europe,
and if you'd like to spend literal hours
going down a rabbit hole of colour theory that I couldn't understand,
you're welcome to use those keywords
as a starting point to your research, but the basic idea is:
this wall is white, and therefore,
the colour that comes out of your screen should also be white.
But if I come back at night, lit by the artificial lighting in the room,
and I don't change the colour settings on the camera...
...this looks very, very yellow.
Because artificial light usually has less blue in it.
Maybe that's because it's imitating old firelight and candlelight
and it feels more comfortable somehow.
Maybe it's just because that was how old light bulbs happened to work.
That yellow-blue distinction is called "colour temperature".
Yellow and blue are complementary colours:
remove one and you'll start to see more of the other.
If you're working with cameras,
colour temperature is something you have to watch out for,
because colours seen on a screen are out of context,
the audience is used to seeing certain wavelengths from their screen as "white",
no matter the lighting used in the room.
So the video colours have to be adjusted to match the light,
so this wall still looks white to you.
I didn't change the lighting just then, only the colour settings on my camera.
Or, actually, in my editing program.
But if I take these new settings back to daytime and sunlight...
...it looks very, very blue in here.
To be clear, in person this is always obviously a white wall.
Your brain establishes colour from context.
Which is why my hoodie looks grey against something brightly coloured,
well, as brightly coloured as you can get in the British countryside
when spring hasn't quite arrived yet,
but against something that's also grey or white...
...maybe not so much.
Because there's one other factor here:
if your clothing is slightly yellow,
it looks stained and tired.
Because usually, slightly yellow clothing is stained and tired.
There used to be a common product called "laundry bluing".
It's mostly obsolete now with modern detergents,
I actually couldn't find it in shops around where I live,
but it added a hint of blue dye to your washing.
If your white shirt is actually very slightly blue,
it can trick the eye into thinking that it's cleaner and brighter and whiter
than the actually-white shirt of the person you're competing with for that promotion.
So maybe, if a company's selling a grey hoodie,
their customers will look better and like the product a little bit more
if it is ever so slightly blue.
And as a personal choice,
when I tweak the colour temperature on my camera or in my editing program,
I'm going to favour going just ever-so-slightly towards blue, partly for that reason,
and partly because I like the way it looks.
Now, I would call this hoodie "grey".
Even if it might seem to have a bit of blue in it.
It's all subjective anyway.
But there is a way to get some sort of definitive, objective answer.
A calibrated colour sensor.
It will light up my hoodie with very precise amounts of light,
and measure the wavelengths that are coming back into its sensor.
Which means it can give me calibrated colour numbers,
but it'll also match the colour
to the descriptive names that paint companies use.
Which means that if I test it on this spare hoodie, the colour is...
...Amethyst Sky.
I'm not sure that's helpful.