- [Voiceover] YUV color is the light,
sometimes called the luma,
then the blue and the red.
The green is worked out based on those two colors.
In fact, what I'm describing now
is technically called YcBcR.
That's luma and the color blue and color red,
but people often use these terms and others interchangeably
without any clear idea about the difference.
Actually, YUV uses a specific scale,
a graph if you prefer,
with U and V as readings on that scale.
YcBcR is quite a lot to say,
so we use the term YUV as a more general reference
to an approach that puts luma in one channel
and colors into other channels.
In video editing systems, it's usually the luma,
that's measurable light,
the amount of blue and the amount of red,
or some other two color channel combination
that represents the color in the pixel.
The important distinction for me is that
one system just measures color, that's RGB,
and the other system separately measures the luma,
but when I'm speaking about these things,
what's going on in the pixel.
Until now, I've been speaking about RGB,
which is a straightforward system to imagine.
Genuine YUV makes more sense with a graph.
We're still talking about three channels,
but now one of them measures the luma,
one measures the U-axis on a graph,
and the other measures the V-axis.
Back in the analog days,
this was a cleaver way to effectively get
four signals from the three.
The red, green, and blue colors are on the graph,
so you only need a kind of crosshair approach
to choose the color you want.
That's the U and the V.
And then a separate signal captures the luma.
In fact, this is a fairly close match
for the way human vision works too.
Our eyes are much better able to detect the luminance
in an image than the color.
So it makes sense to focus on
getting that part of the image right.
Our perception of color is so bad
compared to our perception of light
that most recording systems skip recording color information
for at least half of the pixels in an image
and we don't notice.
More about that in the lesson about color spacing.
YUV is an efficient system also because
when transmitting an analog signal,
the more you break the signal into it's component parts,
the less cross signal interference you get.
In a nutshell, the picture arrives cleaner
because the different radio signals
don't effect each other as much during transmission.
The idea of keeping the signal cleaner
works mathematically too.
It needs less information to capture a more precise image,
and this is useful of course when we're working digitally.