Additive/Subtractive

[kathleen]

Paulette,

zackly! I have had the same thought re the fact that, well, that's where the facts are. (Physics, I mean)

i have been especially befuddled by a lifetime of believing yellow and blue make green not being true anymore. I really don't understand why and have trouble believing that - what is it - red and green? making yellow? can this be?

apparently, but at this point it is more an item of faith than understanding.

I will have to add your link to my list of those with which i am trying to enlighten myself.

thanks

[DJ Dubovsky]

Thank You Kathleen!!! I thought I was the only one who still believes the primarys are red, blue and yellow and the secondarys are violet, orange and green. From kindergarden on, it has been drummed into our heads. Trying to unlearn that is like changing religion or something. Why is it when we paint we mix yellow and blue to get green but now when the printers mix ink it's cyan and yellow. That has been the single most difficult thing to comprehend (or unlearn) since I started this Photoshop thing. I'm glad you voiced that one.
DJ

[kathleen]

sistah!

p.s. e=mc x mc (how do you make "squared", anyway?)

[DJ Dubovsky]

Same way you make "degrees", spell it out. Maybe we should form our own little "color club" for all those die hard fans of the red blue yellow system.
DJ

[kathleen]

sign me up

but really, i'm sure there is an explanation for why what is true for paint is not true for light and it prob. lies in physics, which i never took.

more than one child i taught "blue and yellow make green"; a few breaths later i taught "black makes colors sing" (that from a quilter's book on color theory). i'm glad at least one of the two statements is reliable.

[Doug Nelson]

Well, you gots your "additive" colors, for light (RGB) and your "subtractive" colors, like for paint and ink (CMY).

R+G+B=White
C+M+Y=Black

Now who is this Roy guy, and what's a gbiv?

[DJ Dubovsky]

I got no problem with those additive colors. I just want to know why my paint and their inks (which are pigments) do not work the same. Other than that, I'm cool.
DJ

[kathleen]

yeah. yeah. thass right. way to ask it. tell me that. just tell me that.

[Doug Nelson]

What was the question again?

No, seriously.

[Ed_L]

Once again, I might be wrong, but it makes for conversation . I think the difference is in the colors created by reflective light vs. transmitted light. Red + yellow = orange. Wanna bet?

Ed

[kathleen]

red + yellow = orange is the truth as i used to know it. yellow doesn't make the cut any more for primary.

i think what dj meant is: why is ink not equivalent to paint? yellow plus red in paint equals orange, why not in cymk?

i'm sure it is about light @ it's heart, i read something once that made me think that it had to do with paint being opaque "stuff"; all real vague to me, and, i'm also sure full of physics and stuff i will have to squint to understand.

[DJ Dubovsky]

Exactly!!
DJ

[Doug Nelson]

Well, just out of curiosity, what combo of C, M, and Y makes red? And if you add Y to that, is it orange?

[DJ Dubovsky]

Magenta and yellow. Figure that one out Here's a red with a little purple in it mixed with yellow to get pure red. Oh wait a minute Purple and yellow cancel each other out because they are opposites and you are left with the red. Now I get it....No I don't.

OK Kathleen, you started this mess. Now we're really confused.
DJ

[Doug Nelson]

So equal parts M and Y make 'red'...add some more Y to 'red' and you get orange. Where's the confusion?

[Ed_L]

Huh?

[DJ Dubovsky]

The confusion is why start out with magenta to begin with. Why not just mix red and yellow for orange instead of magenta, red and yellow.

I think I'll stick with paints. I understand those better.

I'm with you ED
DJ

[Doug Nelson]

Red=R, M=Magenta, Y=Yellow, O=Orange

R=(1xM)+(1xY)
O=((1xM)+(1xY))+(1xY)

In the subtractive color system, red is made up of contituent parts, you add more yellow to those parts and get orange

Paint=thick ink

The confusion lies in mentally mixing up two color systems. "Primary Colors" mean the base colors that all other colors are made from (in a given system). Magenta isn't 'red with a little purple in it' in the subtractive system, it's one of the three pure colors.

I'm really sorry if I'm messing you guys up with this left-brain stuff.

Someone post a great link explaining color theory here and bail me out

[Ed_L]

I think you're just enjoying toying with us on your birthday. :p

Ed

[thomasgeorge]

Gee, Black and White type stuff is becoming increasingly attractive!! Tom

[DJ Dubovsky]

When color equasions start looking like algebra, I quit. I think I will just stick with my tried and true method...if it looks good you did it right, if it don't, try another color.
DJ

[paulette conlan]

Great thread. I've really been confused on the color stuff. Anyway, I found a link that explains it well.Now I finally understand why in RGB( the visible spectrum) Red+Green =yellow . As I understand it,i t's because the monitor emits light and handles color differently than the traditional way we learned color for painting and printing on paper.Basically, we're talking about two different ways that color is handled. One way where light is reflected and the other way is where light is absorbed.Anyway, Kodak does a great job of explaining it on the link. On to the pixels and vectors!
http://www.kodak.com/US/en/digital/d...olorM2_5.shtml

[kathleen]

On to the pixels and vectors!

hush yo mouff, honey chile (you speak southern, right? )

onward and upward, thanks for the link paulette

[Ron]

Hows this for a thought…
As Doug said earlier “additive” colors R255+G255+B255=White. Referring to your monitor, which is based on light, the absence of any color is Black and the “addition” of color gets you closer to White. Keep in mind that your monitor produces color by shooting Red, Green and Blue guns onto a black screen. (As it turns out the color gamut of monitors does not include a good representation of Cyan, Magenta or Yellow)

Conversely “subtractive” colors C+M+Y=Black. Referring to your Printer, which is based on reflective light, the absence of any color is White (the paper) and the more color you add “subtracted from white” gets you closer to Black. Therefore less ink gives you lighter colors and the addition of Black gives you darker colors. (Unfortunately the color gamut of CKYM printers does not include true Blue, Green, or Red).

Is it any wonder we have a lot of color problems when monitors can’t accurately reproduce printer colors and printers can’t accurately reproduce monitor colors?

For the complete story visit http://www.nebulus.org/tutorials/2d/pictpub/colormerge/
for a two part “in depth” tutorial on color and color management

Ron

[Doug Nelson]

An excellent explanation.

[Ron]

Thanks Doug but I believe I missed the mark a bit. The original question was about color (Red & Green = Yellow)

Given that paint & ink are reflective colors they operate the same way we learned in school. (Blue & Yellow = Green) and (Red & Yellow = Orange).
Color printers set their primary colors as Magenta, Cyan, & Yellow. Why. Because they need a color model that will display as many colors as possible using three ink colors. Combining "White" paper plus "Black" ink gives an incredible color capability to printers. Using normal color theory, printers mix Cyan + Yellow + Black to make Green.
(Using Red, Blue & Yellow inks would not give the same color range capabilities).

The Red, Green, Blue, color model utilized by our monitors however, use a color model we never learned in school. This model starts with a black screen and electrons from three "guns" are targeted on groupings of Red, Green & Blue dots. When these three "guns" fire electrons at all three dots at maximum intensity "white" is created. Varying the "guns" being fired and the intensity at which they are fired create different colors. Maximum "White" = R-255, G-255, & B-255. Maximum "Red" = R-255, G-0, & B-0. Maximum "Black" = R-0, G-0, & B-0. etc… In this color model if we start with "White" = R-255, G-255 & B-255 and remove all the Blue (R-255, G-255 & B-0) we are left with "Yellow".
To see this for yourself open Photoshop and make a new image with a white background. (The "Mode" will be grayscale so change the "Mode" to RGB) Now go to Image\Adjust\Levels. Select the "Red" channel and with "Preview" selected, use your mouse to move the small triangle at the right of the black/white gradient display. This varies the Output Level of the "Red" channel. As you remove the output of the "Red" channel (removing the red) your image will turn "Cyan" in color. [Reset the "Red" Output to 255].
Now change to the "Green" channel and adjust its Output Level from 255 to 0. Now you will see your image turn "Magenta". Doing this in the "Blue" channel will turn your image "Yellow". This demonstrates that "Red" plus "Green" (no "Blue") = "Yellow"

Hope this helps a bit

Ron