Alexander Image wrote:
A color in a light is totally different from a color in paints. In a light it is subtracted, and in paints it is added.

No, mixing paint is like sandwiching filters. When light bounces off of paint particles certain wavelengths are absorbed (similar to the multiply blend mode in Photoshop) - when the light strikes particles of the other color more wavelengths are absorbed.

Mixing paints can never produce a brighter color than the colors being mixed.

Hector Fernandez wrote:
Its more easy to undestand it with black and white, in one system you create black by mixing all your base colors in the same proportion that would be substractive, in the additive you create white by mixing all the base colors in the same proportion.

In nature the system is additive, time-space is black and sunlight is white.

In CMYK or other printing processes the system is substractive the space is white and you have to create blackness.

All true except the process is not subtraction. It's multiplication.

digital Artform wrote:
No, mixing paint is like sandwiching filters. When light bounces off of paint particles certain wavelengths are absorbed (similar to the multiply blend mode in Photoshop) - when the light strikes particles of the other color more wavelengths are absorbed.

Mixing paints can never produce a brighter color than the colors being mixed.

In a light, three primary color lights are Blue, Red, and Green.
When these three primary color lights are put together, they produce “WHITE” color light
In reality, we use “white” light to produce different “color” lights – subtract


In paints, three primary colors are Blue, Red, and Yellow
When these three primary colors are put together, they produce “BLACK” color
In reality, we use three primary colors to produce different colors - add

Alexander Image wrote:

In a light, three primary color lights are Blue, Red, and Green.
When these three primary color lights are put together, they produce “WHITE” color light
In reality, we use “white” light to produce different “color” lights – subtract


In paints, three primary colors are Blue, Red, and Yellow
When these three primary colors are put together, they produce “BLACK” color
In reality, we use three primary colors to produce different colors - add

First, you know that the 'red' and 'blue' are not the same red and blue between additive and 'subtractive' (multiplicative) models, yes?

In additive the preferred primaries are red, green, and blue

In so-called subtractive models the preferred primaries are red more like magenta, and blue more like cyan.

Alexander Image wrote:
In a light, three primary color lights are Blue, Red, and Green.
When these three primary color lights are put together, they produce “WHITE” color light
In reality, we use “white” light to produce different “color” lights – subtract


In paints, three primary colors are Blue, Red, and Yellow
When these three primary colors are put together, they produce “BLACK” color
In reality, we use three primary colors to produce different colors - add

Next, when you add light you pretty much really are adding it. Get three slide projectors and overlap spots of red, green and blue. They will add to white.

Now 'add' together paint in a mixing bowl and stir it with a spoon and in spite of all that 'adding' you did you are 'filtering' or 'multiplying' (or as many say, 'subtracting') color with every bounce of every photon off every paint particle it hits.

Downtown Pro Photo wrote:
I believe the terms are hold overs from printing from negatives in a dark room.  You could print using either a subtractive head which would mix in Yellow and Magenta filters through a mixing chamber to get the desired color balance for the exposure.

So really it was mis-named early on. And now the name is ingrained.

digital Artform wrote:

So really it was mis-named early on. And now the name is ingrained.

Not so much misnamed as named how it was applied.
With subtractive printing you started with a white light source and then thtough the use of filters "subtracted" the elements of it you didn't need to achieve the correct color balance. 
With Additive printing you started with red, green and blue light sources and added them together to get the mix needed.  Equal amounts of RGB light = White light which gave the base density and very rich blacks.  The variations of the three created the balance required for the color balance.

Downtown Pro Photo wrote:
Not so much misnamed as named how it was applied.
With subtractive printing you started with a white light source and then thtough the use of filters "subtracted" the elements of it you didn't need to achieve the correct color balance.

If filters actually subtracted color then stacking enough of them together would go beyond black and deeper and deeper into 'negative color' - which doesn't exist.

Filtering is like multiplying.

Stack 11 90% ND filters together and you get

.9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 = 0.313810596

ever closer to black.

digital Artform wrote:

If filters actually subtracted color then stacking enough of them together would go beyond black and deeper and deeper into 'negative color' - which doesn't exist.

Filtering is like multiplying.

Stack 11 90% ND filters together and you get

.9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 * .9 = 0.313810596

ever closer to black.

Yes filter don't subtract color (that's why I used quotation marks).  They absorb or block certain wavelengths of the spectrum as light passes through them.
Subtractive just sounds better than absorbtion printing.

Chris Macan wrote:
It is called subtractive color because it subtracts the wavelengths of light and what you see is only the remaining reflected light.
you start with the white base and subtract reflected light until you reach black.

Only multiplication is smart enough to 'turn off' at black and not proceed into negative land.

'Subtraction' is just a poor description of the process of absorption.

If subtraction described the process then a red filter over a yellow filter would produce a very different result than the yellow filter over the red one. Since A - B is very different than B - A.

Whereas A * B = B * A

digital Artform wrote:
Only multiplication is smart enough to 'turn off' at black and not proceed into negative land.

'Subtraction' is just a poor description of the process of absorption.

If subtraction described the process then A red filter over a yellow filter would produce a very different result than the yellow filter over the red one. Since A - B is very different than B - A.

Whereas A * B = B * A

In reality most color we see is absorptive/reflective.
and it is "smart enough" to stop when there is no more light to reflect.

The theory of additive and subtractive color is in reality simply referring to light.
It works perfectly well when applied to RGB or CMY light.
(which is what it was meant for)
However when you start getting into filters and pigments you are getting away from the light and wandering into areas where materials and methods confuse matters.

subtractive is a perfect name for how CMY light works to create black.
Just as additive is a perfectly fine name for how RGB light works together to create white.

You are over thinking things.

digital Artform wrote:
Actually ND filters are a good way to talk about the issue because everyone already knows they are not subtractive.

Actually they are not..... because they are not.
you have departed from color theory and are trying to prove you argument with something else.

Chris Macan wrote:
Actually they are not..... because they are not.
you have departed from color theory and are trying to prove you argument with something else.

A filter is a filter whether it absorbs every wavelength approximately equally (like an ND filter) or some frequencies more than others (like a gel)

It's all the same thing.

Alexander Image wrote:
“Subtraction” descripts the functionalities of a filter to a light.

No, for reasons explained above.

Chris Macan wrote:
Actually they are not..... because they are not.
you have departed from color theory and are trying to prove you argument with something else.

Stack numerous red filters, then if you prefer.

Will a 50% red on top of a 50% red make 100% ? No. It will make a 25% red.

Try it.

digital Artform wrote:
No, for reasons explained above.

There are many filters, and “ND” filter is just one of them. It doesn’t affect colors or we could call it as  “white” filter if you like.

Alexander Image wrote:
There are many filters, and “ND” filter is just one of them. It doesn’t affect colors or we could call it as  “white” filter if you like.

There is nothing special about an ND filter vs a red filter except that an ND filter tries to multiply down all wavelengths equally.

Note, I said it 'tries' to. There is no perfect one. They are ALL colored to some minute degree.

a polarizing filter is another matter.

digital Artform wrote:

There is nothing special about an ND filter vs a red filter except that an ND filter tries to multiply down all wavelengths equally.

Note, I said it 'tries' to. There is no perfect one. They are ALL colored to some minute degree.

a polarizing filter is another matter.

How does a red filter work?

Alexander Image wrote:
Here we are talking about “subtractive color”. So the filters we are talking about are  “color” filters!

First of all, as I just explained, an ND filter IS a color filter. Just a weak one.

Second, if you prefer a strong color filter, I already covered that...

digital Artform wrote:
Stack numerous red filters, then if you prefer.

Will a 50% red on top of a 50% red make 100% ? No. It will make a 25% red.

Try it.

Alexander Image wrote:

How does a red filter work?

The same.

digital Artform wrote:

Alexander Image wrote:
Here we are talking about “subtractive color”. So the filters we are talking about are  “color” filters!

First of all, as I just explained, an ND filter IS a color filter. Just a weak one.

Second, if you prefer a strong color filter, I already covered that...

What color light source are you talking about?

Alexander Image wrote:
What color light source are you talking about?

It doesn't matter, but to maximize our perception of the effect lets say white light.

digital Artform wrote:

It doesn't matter, but to maximize our perception of the effect lets say white light.

White light!
So after it goes through a red filter, what color of light is it?

Chris Macan wrote:
Actually they are not..... because they are not.
you have departed from color theory and are trying to prove you argument with something else.

digital Artform wrote:
Stack numerous red filters, then if you prefer.

Will a 50% red on top of a 50% red make 100% ? No. It will make a 25% red.

Try it.

You are once again not talking about light...
but how colored glass affects light.

It is not the same thing

Alexander Image wrote:

White light!
So after it goes through a red filter, what color of light is it?

It's white light with all the wavelengths except the long ones knocked back a percentage so that it appears a shade of red equal to the filter.

Now what do you think happens when it goes through an identical red filter a second time? You think it remains unchanged?

Chris Macan wrote:
You are once again not talking about light...
but how colored glass affects light.

It is not the same thing

So lets talk about light, then.

Unfortunately I have to run. But I'm happy to resume later.

Challenge me on some point and I'll see if I can answer it after my shower but before I leave.

digital Artform wrote:
It's white light with all the wavelengths except the long ones knocked back a percentage so that it appears a shade of red equal to the filter.

Now what do you think happens when it goes through an identical red filter a second time? You think it remains unchanged?

Yes! Changed! Changed! Changed!
Why???
Because the filter subtracted some colors of the WHITE light!