primary colors

CMoore · Oct 23, 2015

1. Was not sure where to ask this.
2. I searched the Internet, but it brings a huge respose of options. I am sure it is pretty basic, so pardon me for asking.

In photography, I always read that the primary colors are
Red
Blue
Green
If you mix Green and Red you get mud. Is that some type of...not even sure what to call it...subtractive light wave theory.?
I painted for a living and often had to match Paints and Stains. The primary colors in the world we see are
Red
Yellow
Blue
You get Green by combining Yellow and Blue.
So finally, my question is...why is Green a Primary Color in photography.?
Thank You

Dr Croubie · Oct 23, 2015

RGB are primary Additive colours. As in, you add light together.
CMY are primary Subtractive colours. As in, you mix paint together, paint subtracts light and reflects whatever colour it is.

Add Cyan and Yellow Paint together, you get Green Paint. Cyan paint subtracts red from white light and reflects cyan. Yellow paint subtracts blue from white light and reflects yellow. Green paint subtracts both red and blue light and reflects green.

Mr Bill · Oct 23, 2015

No quick answer, but some background first. In photography, we call red, green, and blue ADDITIVE primaries, as in combining these colors of LIGHT. What we generally have in our prints is a set of dyes called cyan, magenta, and yellow; they are the "complements" (similar to opposite) of r, g, and b, and are known as SUBTRACTIVE primaries, and act like filters in a light path. These are functionally more similar to an artist's primaries.

Now if you consider the somewhat vague definition of a color, such as "red," you can probably see that the artist's "red" might actually be the same thing as the photographer's "magenta," etc. Likewise blue vs cyan, and both use the same yellow. In other words, I think that the artist's primaries are essentially very close to the photographer's SUBTRACTIVE primaries.

I see that Dr Croubie is much quicker than I, but since I have already typed this, here it is.

OzJohn · Oct 23, 2015

Dr Croubie said:
RGB are primary Additive colours. As in, you add light together.
CMY are primary Subtractive colours. As in, you mix paint together, paint subtracts light and reflects whatever colour it is.

Add Cyan and Yellow Paint together, you get Green Paint. Cyan paint subtracts red from white light and reflects cyan. Yellow paint subtracts blue from white light and reflects yellow. Green paint subtracts both red and blue light and reflects green.

That is the most succinct and useful explanation of additive versus subtractive colour that I've yet read. I've seen people rabbit on for paragraph after paragraph trying to explain it. OzJohn

David Allen · Oct 23, 2015

The primary colours are indeed Red, Blue and Green. These are some of colours that we can see and are part of a much larger electromagnetic spectrum. If you mix equal quantities of Red, Blue and Green you will get (depending upon the quantities of each) either white or a shade of grey. By varying the amounts of Red, Blue and Green you will be able you to produce every colour that we can see.

When most people refer to primary colours they will cite Red, Blue and Yellow. This is because they have been incorrectly taught at school that these are the primary colours when they are in fact the primary pigments. This can clearly be demonstrated by the fact that Red, Blue and Yellow can only produce some of the range of colours that we can see. No combination of Red, Blue and Yellow pigment can produce a pure Black or White (this is only achievable by not applying any pigment to white paper).

Similarly, in the world of printing with inks the primary colours are Cyan, Magenta and Yellow. No combination of Cyan, Magenta and Yellow pigment can produce a pure Black (this is only achievable by adding a fourth ink - black) or White (this is only achievable by not applying any ink to white paper).

Photography and photographic materials are based on light and what we see is the result of light hitting the retinas in our eyes. Therefore, the primary the primary colours in the world that we see are the colours of light and these are Red, Blue and Green.

Bests,

David.
www.dsallen.de

CMoore · Oct 23, 2015

Wow...OK.
As a painter, we never thought much about light. You mixed the colors in the light where they would be used...it just does not get much thought.
Even the architects downplayed the LRV of paint colors, even though it would be in their specs.
Two different worlds.
Some Really Great Info
Very Well Said
There are some real sharp members on this forum.
Thanks Again

RobC · Oct 23, 2015

how they mix, or rather how they filter out their opposites.
View attachment 118658

I corrected my error in the mixing of the secondaries.

AgX · Oct 23, 2015

There is the terminology of the photographer/light scientiest and that of the painter, which are not compatible.

Also there can be interaction between additive and subtractive effects in paints.

Best read a good(!) textbook (by Hunt) on this matter and you may have a look into the Küppers theory too

RobC · Oct 23, 2015

Its really very easy. Just remember that the operative word is "Filter" becasue thats what happens. The filters filter out their opposite colours.

Cyan filter only transmits Cyan so it filters out Red (Magenta and Yellow)
Magenta filter only transmits Magenta so it filters out Green (Cyan and Yellow)
Yellow filter only transmits Yellow so it filters out Blue (Cyan and Magenta)

Red filter only transmits Red so it filters out Cyan (Blue and Green)
Green filter only transmits Green so it filters out Magenta (Red and Blue)
Blue filter only transmits Blue so it filters out Yellow (Red and Green)

Fr. Mark · Oct 23, 2015

See the handprint.com website designed for watercolor painters but has the best survey of texts and general information color theory and pigment mixing, human perception, etc., I've ever seen. When I paint its oils, but the info there is very very helpful and thorough. Another resource is http://www.gamblincolors.com/navigating.color.space/ again, aimed at painters but very very helpful.

frank · Oct 23, 2015

What about magenta?

Gerald C Koch · Oct 23, 2015

The OP is on track with his question. Anyone who is serious about photography should be familiar with the color wheel. Not only is it important in color photography but also B&W. What color filter is used in B&W can be determined from the color wheel and what colors you want to emphasize.

Old-N-Feeble · Oct 23, 2015

frank said:
What about magenta?

I've heard it on great authority that magenta is not a color.

gone · Oct 23, 2015

No matter what your wife said, magenta is a colour.

http://www.google.com/imgres?imgurl...ved=0CCUQ9QEwAGoVChMIjOn-4PbYyAIVgi8mCh3tWwSP

Black is not a colour, it's the absence thereof, as it absorbs all light and reflects none. Painters need to understand subtractive and additive light too, especially if they work w/ watercolours, but painters don't do much thinking, at least if they're any good. If you think about it, you're screwed. Just get it done, and if it looks right, it is right. Theories are for those that can't do.

Old-N-Feeble · Oct 23, 2015

There's no such thing as black because, unless the universe ceases to exist, at lease some radiation will be present, little as that might be. My wife tells me nothing... I divorced that nut-case long ago.

frank · Oct 23, 2015

momus said:
No matter what your wife said, magenta is a colour.

http://www.google.com/imgres?imgurl...ved=0CCUQ9QEwAGoVChMIjOn-4PbYyAIVgi8mCh3tWwSP

Black is not a colour, it's the absence thereof, as it absorbs all light and reflects none. Painters need to understand subtractive and additive light too, especially if they work w/ watercolours, but painters don't do much thinking, at least if they're any good. If you think about it, you're screwed. Just get it done, and if it looks right, it is right. Theories are for those that can't do.

An ant stopped a millipede that was walking by and asked,
"With so many legs, how do you keep from tripping up?"
The millipede started to think about it, and never walked again.

gone · Oct 23, 2015

It's even trickier. White LIGHT is not a colour, but it requires three different colours (or light, at three different frequencies) for it to appear. If you mix three primary light colours you will not get black, you will get white. Nor sure if this is additive or subtractive or neither, it is just good to keep in mind.

Sorry about my assumption. Around here, the wife is the source of Great Authority. I do what I want, when I want, I just like to run it by her first. THEN I do what I was going to do, regardless. That way I can say, don't you remember, we discussed this some time back! If she still has a hissy fit, I then say OK, I'll do it your way, but I don't want to, and don't think it's right. Then she says, well, OK, we'll do it your way. Relationships are complicated. There's an art to this thing. Her tactics are much better than mine because I have no idea how hers work. They're probably so good that she gets me to thinking I'm getting my way, when in reality.....

RobC · Oct 23, 2015

Old-N-Feeble said:
There's no such thing as black because, unless the universe ceases to exist, at lease some radiation will be present, little as that might be. My wife tells me nothing... I divorced that nut-case long ago.

Well actually there's no such thing as colour. Colour isn't a physical property of any substance or of the electro magnetic spectrum. Colour is a human perception and exists only in our minds. Black is one of those perceptions and is therefore as valid as any other "colour" which doesn't exist in nature. It just happens to be what we perceive when there are no electro magnetic wavelengths in the so called "visible spectrum" reaching our eyes. And infact a true black body which emits no wave lengths exists only in labs and in space. Any objects we see and call black here on earth aren't black at all, we perceive them as very dark grey which we call black.

frank · Oct 23, 2015

I buy used gear so when my wife asks if that is a new camera or lens, I can say, "No it's old."

Old-N-Feeble · Oct 23, 2015

Right, you are, Rob. Color is a human descriptive of a form of energy we perceive via the receptors in our eyes and interpretation of that energy by our brains. So... hmm... magenta really DOESN'T exist.

DREW WILEY · Oct 23, 2015

Maybe they told you red, blue, and yellow are primaries in kindergarten, but that's never been the case in actual color theory, color mapping
or true color matching. That's neither how human vision works nor how actual pigment mixing. Even modern matching spectrophotometers of pigments simply interpolate CIE color mapping using analytic geometry programs, whether they're basic $20,000 units like I once used or
the six million dollar one my wife used in a research facility. Same with inkjet printer programs. On the other hand, SUBTRACTIVE colors in
the color printing sense are, and always will be, those directly complementary on the color wheel to the primaries, and consist of yellow,
magenta, and cyan. For example, I own both additive color enlargers (RGB, best color, but tricky to make and use) and more ordinary subtractive ones (YMC). But tone (whiteness) or tint (blackness) can be calculated either on a single plane from one extreme to another
in terms of brightness (three-dimensional color mapping) or by calculating tone and tint separately (four dimensional color mapping).

DREW WILEY · Oct 23, 2015

Not exactly, Michael. You have to choose the time of day and angle of sun, time of year etc per the color temp preference. So I matched the
sunset side, for example, to how it looked when I got home to work, since in the morning its mostly foggy and soft-box lit, but otherwise
bluish light. But in the afternoon, the blue trim received warmer color temp than the blue porch, which was already in shade, so I mixed to
blues differently, yet to appear the same to the eye, based on respective color temp. But this was easy and my house is pretty modest.
But when I was actually getting paid to do a color consult for some multimillion-dollar Victorian restoration, for example, those color temp
tweaks were incorporated all over the place. Then I'd sign on to do the large format shoots before and after, and it gave me a pretty nice
tweak of income. Many of these were redos of bellyflop color schemes by alleged pros who didn't understand the nuances of outdoor light.
The most blatant case was one who specificed a deep blue/scheme of a classic Victorian farm mansion. But he never visited the location itself, which happened to be right in the middle of a bright green alfalfa field. Both the inherent color clash, and the green reflections off
that field onto the paint were a nightmare.

RobC · Oct 23, 2015

You can always do this so that you have corrections fo all colours covered as the light changes...

http://www.thatericalper.com/wp-content/uploads/2014/09/John-Lennons-Glasses-2.jpg

alanrockwood · Oct 23, 2015

Recently I bought a book on the reproduction of color by Hunt. Not exaggerating, it probably has far more than most people here would want to know about color.

One interesting thing about the primary colors is that it is impossible to match all of the colors that a normal person can see by using only three primary colors. Some colors can be matched and some can't. The un-matchable colors vary, depending on exactly how you choose your three primary colors.

As a rule of thumb, those colors that can't be matched can at least be approximately matched, but typically with a reduced color purity.

MattKing · Oct 23, 2015

Michael R 1974 said:
Drew is correct. In fact, he even repaints his house continuously throughout each day so that it always appears to be the same colour as the ambient colour temperature changes.

Not only that, he uses house masks to make sure that the house appears correct when viewed by anyone who walks by.

primary colors

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