Why Do All Printers Use Subtractive Primary Colors (C, M, & Y) ?

Hello:

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?

Is it that the inks are easier to formulate for the subtractive primaries,
or ... ?

This also seems to be true for the big 4 and 5 color lithographic printing
presses.

Curious as to why.

Thanks,
Bob

On Wed, 23 Jun 2004 19:49:09 -0400, Robert11 wrote:
Hello:

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?

Dyes subtract. *always*.

If your injet was somehow emiting light, it could use additive primary
colors.

TCS wrote:

On Wed, 23 Jun 2004 19:49:09 -0400, Robert11 wrote:

Hello:


Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?


Dyes subtract. *always*.

If your injet was somehow emiting light, it could use additive primary
colors.

Think we need not the printer to emit light, but
rather the photo itself.

We need light emitting photo paper

Ken

In article ,
"Robert11" wrote:

Hello:

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?

Is it that the inks are easier to formulate for the subtractive primaries,
or ... ?

This also seems to be true for the big 4 and 5 color lithographic printing
presses.

Curious as to why.

Thanks,
Bob

How would you make the color of inks add? Red ink + Green ink + Blue
ink isn't white.

Some printers do have more than CMYK to improve the gamma, color
intensity, or reduce dither intensity. There can also be specialty inks
like metallics, ultra-whites, glossy and flat blacks, and fluorescents.

On Thu, 24 Jun 2004 00:03:08 GMT, Ken Weitzel
wrote:



TCS wrote:

On Wed, 23 Jun 2004 19:49:09 -0400, Robert11 wrote:

Hello:


Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?


Dyes subtract. *always*.

If your injet was somehow emiting light, it could use additive primary
colors.

Think we need not the printer to emit light, but
rather the photo itself.

We need light emitting photo paper

Ken

I have a 19" Princeton EO-900 light-emitting paper on my desk.
In fact, I'm composing this on it now. :-)

Bill Funk
Change "g" to "a"

On Wed, 23 Jun 2004 19:49:09 -0400, "Robert11"
wrote:

Hello:

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?

Is it that the inks are easier to formulate for the subtractive primaries,
or ... ?

This also seems to be true for the big 4 and 5 color lithographic printing
presses.

Curious as to why.

Thanks,
Bob

That's a good question!
Here's a site with explanation of additive and subtractive colors:
http://www.beer.org/~tpark/color.html

Bill Funk
Change "g" to "a"

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?

Is it that the inks are easier to formulate for the subtractive primaries,
or ... ?

This also seems to be true for the big 4 and 5 color lithographic
printing
presses.

Curious as to why.


IIRC, subtractive printing, which nearly all photographic hard copy imagery
is based on, uses only enough inks/dyes/pigments required as it goes.

Additive printing would require the paper already have the chemistry in it
to the max needed and then have the excess removed leaving what is needed
behind. this would make papers more expensive.

Many years ago, one of the original one hour/small studio machines, the
NORD, was additive based. IIRC, the paper was made with dots of the RGB
embedded, as they were exposed, then developed the colors would appear, the
exposure would make that dot accept or receive the color in development.
Its been so long I can remember much.

"Robert11" writes:

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?

Is it that the inks are easier to formulate for the subtractive primaries,
or ... ?

This also seems to be true for the big 4 and 5 color lithographic printing
presses.

It's all in the way that colour is actually controlled. To get a colour
space that covers most colours humans can see, you need a technology
that can control the intensity of at least 3 colours - usually red,
green, and blue.

Suppose you have three bright light sources (like slide projectors)
aimed at the same spot on the wall. Put a red filter in front of one, a
green on the second, and a blue filter on the third. By putting a
neutral-density filter or a variable-sized aperture in the optics of
each light source, you can regulate the amount of red, green, and blue
light reaching the wall. This lets you create almost any colour.

This method is called additive colour synthesis, because the three
colours follow different paths, are controlled individually, then added
together at the end. CRTs create colour this way, as do LCD displays.
A few colour enlarger heads work this way too.

Now suppose you have just one light source, and only one light path.
The only way you can control red independently of green and blue is to
use cyan filters. Cyan passes green and blue unaffected, but changing
the darkness of the cyan dye controls the amount of red light getting
through. Similarly, magenta filters control green without affecting red
and blue, and yellow filters control blue without affecting red and
green. Each filter passes 2/3 of the spectrum and controls 1/3, so you
get independent control of red, green, and blue, even though all the
filters are stacked together.

This would not work at all for red, green, and blue filters, since they
pass only about 1/3 of the spectrum. Red and green filters stacked in
sequence produce black, or something close to it, since no light passes
freely through both.

The control of colour via sequential filters is called subtractive
synthesis, because each filter subtracts something from the light. Any
image technology that stacks 3 filters in one spot is likely to use
cyan/magenta/yellow primaries: inkjet printing, printing presses, colour
photographic paper. Most colour enlarger heads use subtractive methods
to adjust colour.

Dave

Dave,

See TCS's and Ken Weitzel's replies. The answer to the OP's question lies
in the difference between
emitted light and reflected light. I only direct you to their replies
because your reply sounds like you might be a little confused on the matter
(even though you have a lot of color theory down)...not to slam you.

Have a good weekend,
George

"Dave Martindale" wrote in message
...
"Robert11" writes:

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?

Is it that the inks are easier to formulate for the subtractive
primaries,
or ... ?

This also seems to be true for the big 4 and 5 color lithographic
printing
presses.

It's all in the way that colour is actually controlled. To get a colour
space that covers most colours humans can see, you need a technology
that can control the intensity of at least 3 colours - usually red,
green, and blue.

Suppose you have three bright light sources (like slide projectors)
aimed at the same spot on the wall. Put a red filter in front of one, a
green on the second, and a blue filter on the third. By putting a
neutral-density filter or a variable-sized aperture in the optics of
each light source, you can regulate the amount of red, green, and blue
light reaching the wall. This lets you create almost any colour.

This method is called additive colour synthesis, because the three
colours follow different paths, are controlled individually, then added
together at the end. CRTs create colour this way, as do LCD displays.
A few colour enlarger heads work this way too.

Now suppose you have just one light source, and only one light path.
The only way you can control red independently of green and blue is to
use cyan filters. Cyan passes green and blue unaffected, but changing
the darkness of the cyan dye controls the amount of red light getting
through. Similarly, magenta filters control green without affecting red
and blue, and yellow filters control blue without affecting red and
green. Each filter passes 2/3 of the spectrum and controls 1/3, so you
get independent control of red, green, and blue, even though all the
filters are stacked together.

This would not work at all for red, green, and blue filters, since they
pass only about 1/3 of the spectrum. Red and green filters stacked in
sequence produce black, or something close to it, since no light passes
freely through both.

The control of colour via sequential filters is called subtractive
synthesis, because each filter subtracts something from the light. Any
image technology that stacks 3 filters in one spot is likely to use
cyan/magenta/yellow primaries: inkjet printing, printing presses, colour
photographic paper. Most colour enlarger heads use subtractive methods
to adjust colour.

Dave

"Robert11" wrote in message
...
Hello:

Anyone have a good technical explanation as to why all printers seem
to use subtractive-primary color inks (the Cyan, Magenta, and Yellow) for
printing, rather than the additive primary colors of R, G, and B) ?


RGB is for things that can generate light (like a TV, monitor, projector
etc.) Adding RGB in differing amounts gives a range of perceived colours up
to white. The human eye reacts to RGB stimulus.

A printed sheet of paper has to rely on reflection of ambient light
(illuminant), so all an ink can do is absorb/subtract parts from the
original illuminant to reproduce colours. In a nutshell:

Cyan subtracts Red
Magenta subtracts Green
Yellow subtracts Blue

So (assuming you are starting with white ambient light), you can reproduce
the original RGB values of an image by using varying amounts of CMY inks on
the paper.

A tad simplified, but hope it helps.