- [Instructor] Pixels on a screen glow,
combining different amounts of red, green, and blue
to create the impression of a color.
This means the maximum brightness
comes from the combination of those pixels.
Each piece of color information, that's the
red, green, or blue level,
is referred to as a channel,
and you can think of a channel as a separate signal.
You can use two monaural audio channels
to create a stereo mix,
or three monochrome color channels to create full color.
Keep this word, channel, in mind,
as it's used a lot in reference to
pixel values, radio signals,
audio, or even video streams.
In any case, it'll mean one signal.
The color you perceive
when looking at RGB color information
is created by adding red, green, and blue to black,
from nothing.
This is referred to as additive color,
because you add the red, green, and blue values together
to get the final color.
Gray will always be created
by having an equal amount of all three colors.
If you're working with eight-bit video,
which runs from zero to 255 for each of the colors,
then a value of 100 for all three cameras
will be a darker gray
than a value of 200 on all three channels.
If there's any variation
in the levels of these three channels,
you'll perceive color.
It's a pretty obvious that a value of 100 red,
zero green, and zero blue
will produce a red pixel.
But what about 100 red, 100 green, and zero blue?
It turns out there are some pretty simple rules
for the colors you can expect to see
when you mix different levels of
these three channels.
Green combined with red makes yellow,
blue and green makes cyan,
red and blue makes magenta.
There are a few ways
of describing the relationships
between the colors, graphically.
Perhaps most common is the color wheel.
Notice that much of the color wheel
looks a little indistinct.
Not really a clear yellow, blue, or whatever.
In any case, the various combinations
of red, green, and blue color information
will produce a significant number of unique colors.
In theory, even with eight-bit images,
each pixel can present
more distinct colors than the human eye can perceive.
It's important to note that the idea of
capturing red, green, and blue color information
for pixels is quite a broad one.
The numbers could, in principle,
just go up and up and up and up and up,
but in principle, the limit is either
the maximum amount of color our eyes can perceive,
'cause there's a maximum amount of red
color saturation our eyes will
capture, for example,
or, more commonly,
the limit of the recording system.
Accepting the limitations of our cameras and screens,
manufacturers settled on maximum levels
of red, green, and blue
that could be reproduced reasonably well
on a calibrated display.
By the way, a calibrated display
is just a high-quality screen
that more faithfully reproduces the colors.
Not all screens are as good at displaying colors as others,
just as not all speakers are
as good at reproducing sound as others.
SRGB is a particular kind of RGB,
with limits that work well for screens.
Adobe RGB has bigger limits,
and yes, it was defined by the company Adobe.
But it introduces a little more planning
to make sure you'll see colors reproduced properly,
because most screens are expecting SRGB.
All of this is a very long way of saying
that RGB is red, green, and blue color information.