WEBVTT
Kind: captions
Language: en-GB

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Okay, I'm just going to address the
elephant in the room as I start,

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yep, we are three months into
Britain's third lockdown at the minute,

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uh, I desperately need a haircut,
and there is a sideways wind here, so

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we're just going to have to deal with
what's going on up here.

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According to the manufacturer,
my hoodie is grey.

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That was what I bought.

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I picked the most generic colour possible.

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It's not going to clash with
anything I film against,

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it's not going to blend into
a green screen or a blue screen.

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Although to be fair, if I am filming
under a blank grey sky,

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it can make the shot
look a little dull.

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But if I am filming against a grey sky,

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and we compare the colours between
the clouds and my hoodie...

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then this looks just a little
bit blue. Or maybe purple?

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It looks a bit different in all those thumbnails.

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I mean, technically those aren't
all the same hoodie,

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I've got several,
but they're all identical.

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To explain the magical
colour-changing hoodie,

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we need to talk about
how colour perception works,

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and also about the
history of laundry.

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First up: a brief run through what you
probably already know from school.

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Electromagnetic radiation is a spectrum,

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that includes x-rays and microwaves
and radio waves and visible light.

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The difference between those
types of radiation is the wavelength.

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We have special cells called "cones"
in the back of our eyes, three types of them,

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and each type reacts to a
small set of different wavelengths.

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Which are, oh-so-conveniently,

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the wavelengths that the atmosphere
easily lets through.

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The wavelengths for each type of cone
overlap a bit, it's not precise,

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but it's roughly equivalent
to red, green and blue.

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So if these cells notice radiation
but these mostly don't, you see blue.

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If these and these do,
but these don't? Magenta.

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And if all of them do,
at just the right balance?

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Well, that'll be white, or grey.

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But you have to remember that
colour is not a real thing.

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colours are experiences,
the philosophical term is qualia,

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your brain just creates
colour in your head

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based on the signals
it receives from those cells.

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Depending on the context,

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you can see the exact same wavelengths
as different colours, even at the same time.

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There are a lot of optical illusions
that play with that.

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colour perception isn't just about wavelengths,

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it's about comparing those
wavelengths to everything around.

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A camera doesn't do that,

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as I shall now demonstrate
with a white wall.

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It's daytime as I record this,

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and the camera is set up for the
daytime light that's shining in.

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Bright sunshine.

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Now, there is an official, precise
definition of "average sunlight",

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it's called Illuminant D65,

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it's meant to simulate the middle
of the day in Western Europe,

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and if you'd like to spend literal hours

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going down a rabbit hole of
colour theory that I couldn't understand,

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you're welcome to use those keywords

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as a starting point to your research,
but the basic idea is:

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this wall is white, and therefore,

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the colour that comes out of 
your screen should also be white.

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But if I come back at night, lit by 
the artificial lighting in the room,

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and I don't change the colour 
settings on the camera...

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...this looks very, very yellow.

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Because artificial light usually
has less blue in it.

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Maybe that's because it's imitating
old firelight and candlelight

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and it feels more comfortable somehow.

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Maybe it's just because that was
how old light bulbs happened to work.

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That yellow-blue distinction
is called "colour temperature".

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Yellow and blue are
complementary colours:

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remove one and you'll start
to see more of the other.

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If you're working with cameras,

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colour temperature is something
you have to watch out for,

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because colours seen on a screen
are out of context,

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the audience is used to seeing certain
wavelengths from their screen as "white",

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no matter the lighting used in the room.

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So the video colours have to be
adjusted to match the light,

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so this wall still looks white to you.

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I didn't change the lighting just then,
only the colour settings on my camera.

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Or, actually, in my editing program.
 

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But if I take these new settings 
back to daytime and sunlight...

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...it looks very, very blue in here.

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To be clear, in person this is 
always obviously a white wall.

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Your brain establishes colour from context.

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Which is why my hoodie looks grey
against something brightly coloured,

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well, as brightly coloured as you can get
in the British countryside

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when spring hasn't quite arrived yet,

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but against something that's also grey or white...

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...maybe not so much.

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Because there's one other factor here:

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if your clothing is slightly yellow,

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it looks stained and tired.

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Because usually, slightly yellow
clothing is stained and tired.

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There used to be a common product
called "laundry bluing".

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It's mostly obsolete now
with modern detergents,

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I actually couldn't find it in shops
around where I live,

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but it added a hint of
blue dye to your washing.

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If your white shirt is actually
very slightly blue,

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it can trick the eye into thinking
that it's cleaner and brighter and whiter

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than the actually-white shirt of the
person you're competing with for that promotion.

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So maybe, if a company's selling a grey hoodie,

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their customers will look better
and like the product a little bit more

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if it is ever so slightly blue.

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And as a personal choice,

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when I tweak the colour temperature
on my camera or in my editing program,

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I'm going to favour going just ever-so-slightly
towards blue, partly for that reason,

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and partly because I like the way it looks.

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Now, I would call this hoodie "grey".

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Even if it might seem to
have a bit of blue in it.

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It's all subjective anyway.

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But there is a way to get some sort
of definitive, objective answer.

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A calibrated colour sensor.

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It will light up my hoodie
with very precise amounts of light,

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and measure the wavelengths
that are coming back into its sensor.

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Which means it can give me
calibrated colour numbers,

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but it'll also match the colour

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to the descriptive names
that paint companies use.

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Which means that if I test it
on this spare hoodie, the colour is...

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...Amethyst Sky.

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I'm not sure that's helpful.