OT: Question about RGB color method

J

John Salerno

Sorry for this non-Python question, but since it's computer related I
know you guys will have an answer, and I don't really know where else to
ask. Mainly I'm just curious anyway.

I'm wondering, why do computers use a RGB color scheme instead of the
primary colors? Is there something you can't do with yellow? It seems
weird that RGB can be combined to make all colors, when that's supposed
to be the job of the primary colors. I'm sure there some technical
computer-related reason that it had to be this way.

Thanks.
 
M

Matimus

Sorry for this non-Python question, but since it's computer related I
know you guys will have an answer, and I don't really know where else to
ask. Mainly I'm just curious anyway.

I'm wondering, why do computers use a RGB color scheme instead of the
primary colors? Is there something you can't do with yellow? It seems
weird that RGB can be combined to make all colors, when that's supposed
to be the job of the primary colors. I'm sure there some technical
computer-related reason that it had to be this way.

Thanks.

See the Wikipedia article on primary colors: http://en.wikipedia.org/wiki/Primary_colors

The quick answer is that RGB is a method of additive color mixing, and
RBY is subtractive (and its not really RBY but YCM). Also, the colors
emitted by your monitor are Red, Green and Blue.
 
K

kyosohma

Sorry for this non-Python question, but since it's computer related I
know you guys will have an answer, and I don't really know where else to
ask. Mainly I'm just curious anyway.

I'm wondering, why do computers use a RGB color scheme instead of the
primary colors? Is there something you can't do with yellow? It seems
weird that RGB can be combined to make all colors, when that's supposed
to be the job of the primary colors. I'm sure there some technical
computer-related reason that it had to be this way.

Thanks.

It's a pigment vs. light-beam thing.

Check out http://en.wikipedia.org/wiki/RGB_color_model

Mike
 
C

Carsten Haese

Sorry for this non-Python question, but since it's computer related I
know you guys will have an answer, and I don't really know where else to
ask. Mainly I'm just curious anyway.

I'm wondering, why do computers use a RGB color scheme instead of the
primary colors? Is there something you can't do with yellow? It seems
weird that RGB can be combined to make all colors, when that's supposed
to be the job of the primary colors. I'm sure there some technical
computer-related reason that it had to be this way.

You'll find your answer in great detail at
http://en.wikipedia.org/wiki/Primary_colors. Television sets and
computer screens use the additive color system because they emit light
rather than reflect light. Yellow is a subtractive primary color. The
additive primary colors are red, green, and blue.

-Carsten
 
P

Paul McGuire

Sorry for this non-Python question, but since it's computer related I
know you guys will have an answer, and I don't really know where else to
ask. Mainly I'm just curious anyway.

I'm wondering, why do computers use a RGB color scheme instead of the
primary colors? Is there something you can't do with yellow? It seems
weird that RGB can be combined to make all colors, when that's supposed
to be the job of the primary colors. I'm sure there some technical
computer-related reason that it had to be this way.

Thanks.

See this link: http://www.rgbworld.com/color.html

The "red-yellow-blue" system we used in elementary school art classes
corresponded to the color mixing capabilities available using the
Tempra paint technology at hand. At the RGBworld URL, the web page
shows how paints and inks follow a "subtractive" color system (called
CMY for cyan-magenta-yellow, instead of blue-red-yellow, but close
enough), in that paint reflects a given color by subtracting out all
frequencies that are not that color. So mixing two subtractive
filters follows a subtractive color "algebra".

However, computer monitors do not follow a substractive scheme, but
rather an additive one, by adding brightness along red-green-and-blue
(RGB) dimensions, mixing red and green light to get yellow. This
raises an interesting problem when *printing* a color image. You
cannot just render the RGB colors from the monitor's additive system
into CMY colors on your inkjet printer's subtractive system. Google
for "RGB color" and you will be presented with a long list of
references for dealing with this issue, including several competing
standards on how to handle it. Even the Wikipedia article on RGB
colors is largely devoted to this issue (as opposed to your more
common question).

-- Paul
 
P

Paul McGuire

Ah, the Wikipedia article for "Primary Colors" is much better at
explaining this than the one for "RGB Color". For instance, in the
Tempra-paint-compatible subtractive system, you probably recall mixing
red, yellow, and blue, and getting black, or at least a dark muddy
brown. Conversely, in the additive system of RGB, mixing red, green,
and blue, gives you... white! You've combined all the light there is,
you should get the lightest color of them all.

-- Paul
 
D

Dennis Lee Bieber

I'm wondering, why do computers use a RGB color scheme instead of the
primary colors? Is there something you can't do with yellow? It seems
weird that RGB can be combined to make all colors, when that's supposed
to be the job of the primary colors. I'm sure there some technical
computer-related reason that it had to be this way.

As has been mentioned by others: red/green/blue ARE primaries --
additive primaries; LIGHT primaries. Paint/printers use subtractive
primaries (and, as one art book title states "yellow and blue DON'T make
green") -- subtractive primaries are cyan, magenta, and yellow (look at
any color printer). In a color wheel, the subtractive primaries are
complements to the additive primaries...

Red
Magenta Yellow
Blue Green
Cyan

Notice the triangles RGB and CMY. Red and Blue LIGHT produce Magenta;
Yellow and CYAN (not blue) pigment produce Green.

The center of that circle is black (for pigments) or white (for
light). This is why printers tend to be rather muted compared to what
you see on screen -- remember this diagram is properly a circle --
mixing cyan and magenta to make a blue draws a chord across that circle.
Since the chord cuts inside, it cuts closer to "black"; some photo
printers have started to add true red and blue pigments to produce
brighter shades.
--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/
 
J

John Salerno

John said:
Sorry for this non-Python question, but since it's computer related I
know you guys will have an answer, and I don't really know where else to
ask. Mainly I'm just curious anyway.

I'm wondering, why do computers use a RGB color scheme instead of the
primary colors? Is there something you can't do with yellow? It seems
weird that RGB can be combined to make all colors, when that's supposed
to be the job of the primary colors. I'm sure there some technical
computer-related reason that it had to be this way.

Thanks.

Thanks guys! This is fascinating...just something I've never really
thought about before. The Wikipedia article will give me something to
read while I'm bored at work! :)
 

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