primary colors

[DREW WILEY]

It gets way more complicated that all of that. You have to know not only about color physiology and things like simultaneous and successive
contrast, advancing and receding colors, stacking them for architectural effect etc, but specific pigment metamerism, how the color will interact not only during different diurnal cycles or season, but in relation to each other as certain pigment fade or shift over time, and thus
the specific recoat cycle. It goes on and on. I also was consulted on lots of the restoration techniques. I avoided the old-money mansions
because a lot of them used old world techniques in the first place, and need those kinds of people brought over from Italy and so forth if
an authentic re-do is involved, with all that goo-gaw moulded plaster, real gold leaf etc. I have been involved in a lot of Julia Morgan redos,
Maybeck, Frank Lloyd Wright etc. The most interesting but disgusting project was Janis Joplin's mansion. It was like walking into Salvador
Dalis brain. I refused to attend the party once the job was completed, because everyone there was seeing colors that had nothing to do
with the paint.

 

[CMoore]

Yeah...the proverbial can of worms.
The primary colors for a painter are simply too removed from photography to be relative.
As simple as it seemed to me at first thought, they are not even close.

As Rob C points out, B&W Photography is about Filtering.
Painting is about mixing, and 95% of the time we are going into white, or a white base. The only time I ever mixed staright colors was when I had to touch up wall covering, faux painted surfaces, graining.....stuff like that. Typically we are using squeeze colors into 1-5 gallons of white(ish) paint.
So I, kind, conflated two completely different aspects of color.
But if I had not asked, I would still be wondering, Red Blue Green, WTF.......

 

[AgX]

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.

To put it in short:

"The rays are not coloured"
(W.D. Wright)

 

[DannL.]

If not already mentioned, take a peek at your computer monitor screen with a loupe. The RGB bars on my Sony Bravia run horizontally, whilst the bars on my HP laptop run vertically. You can see how a back-lit color group of the Red, Green, Blue works quite well.

 

[DREW WILEY]

There is no such thing as black in pigment. For example, lampblack might look black in high density, but added as a tint actually renders a
purplish cast. Mineral blacks trend greenish. Film has its own issues. Velvia actually has quite a few more steps of density than most people
realize. But it's hard to recover them in print fasion, so all the lower zones simply print whatever black a particular medium is capable of.
But then somebody does a high-quality drum scan and finds out those deep blacks are really bluish. One can either fight all this or just learn how to best use it. Normal subtractive colorhead have a bit of residual spillover into white light which slightly contaminates all the colors. Going narrow-band additive RGB filters solves this problem, but due to their greater density require way more light = more heat, and then dichroic filters change their spectral sensitivity with heat. You can either call all this complicated or a fun challenge. Sometimes it was fun to print the same image with both an additive colorhead and a subtractive to see the difference. But theory wise, Van Gogh knew it all, just like any competent painter, even a true profession house painter, if you can find one of those. They constitute about 2% of those out there, at least in this part of the world. The rest are drunks. But that is rapidly changing as a younger crowd has learned how to use
better equipment and skills and get the business.

 

[Gerald C Koch]

There is no such thing as black in pigment.

In Chinese sumi-e (ink-wash) painting different inks are used made from two different types of wood burned to charcoal. One charcoal produces a black with a slight bluish cast while the other produces a brownish cast. The difference in color is highly prized by those who practice the art.

 

[DREW WILEY]

That's fascinating. I was aware of their technique of selecting certain kinds of wood planks, flaming them, and then rubbing it down for a differential grain hue. Here we call that arson. But they have finesse. As I understand it from some of my customers who have lived in Japan
to learn some of those techniques, they'll pay a bundle for a prized piece of North American yew for its fire-finishing characteristics.

 

[DREW WILEY]

Sorry about mixing up Japanese and Chinese technique, but they are related, and I have friends who studied in China as well. My wife studied
a full year in the University of Beijing and was the first American student to ever take a class from their most famous living calligrapher.
She wasn't very good at it, but he was so thrilled at having an American student that he gave her several scrolls. The subtle color differences
of the sumi inks is apparent.

 

[Sirius Glass]

What about magenta?

Magenta is not a color according to some. :devil:

 

[Sirius Glass]

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

+1

 

[RobC]

Magenta is not a color according to some. :devil:

What about Fuchsia and Aqua Marine? :devil:

 

[MattKing]

And of course, everyone should say after me: "Roy-gee-biv"

 

[DREW WILEY]

Guess most of you haven't worked with pigment much. A lot of art lore tradition was based on the fact that there was nothing around which
matched an ideal blue or green or yellow. Chromium oxide was pretty dirty (like the greens in early Ektachrome 64). Then pthalo green was invented, but horribly blue contaminated. Most permanent actual yellows are toxic as heck. People who had the Pope looting all of Germanyto finance a chapel ceiling could afford to buy pure ground lapis blue and a similar green, which even to this day is more expensive per ounce than gold dust. What people think of as American Colonial colors, specifically George Washington's sitting room in Mt Vernon - a drab rusty hue - was actually psychedelic bright green true copper verdis gris. But that's starts oxidizing in less than two years. Fresco painters chose natural pigments that don't fade. If you want to see that mineral pigment selection, look at the surface of Mars.

 

[CMoore]

There is no such thing as black in pigment. For example, lampblack might look black in high density, but added as a tint actually renders a
purplish cast.....

Blue cast actually.
All our squeeze colors were heavily shaded.
Light Yellow was very blue.
Medium Yellow was quite red.
Chromium Green was quite blue while Medium Green was rather yellow.
We use to have colors called Mars Black and Drop Black which were much closer to "real" black.
As a painter we never really mix true colors, we were always matching some wall color from one of the many paint stores. Not too many people want a Red wall or a Blue wall...not in the color wheel sense of the colors.
A tube of Permanent Violet would go off before we ever used it all.
Green was another color that never got used much.
Raw Umber and Light Yellow made a color about as Green as you ever got from a paint store.....always exceptions of course.
Interesting discussion. As others have said, color is defined by light. When the sun goes down, everything starts to lose its color and become an object of Blacks and Whites.

 

[Fr. Mark]

Drew, Re: toxicity you are supposed to color things with paint not be like Van Gogh and eat them!
properly handled Cadmium Yellows (and reds) are safer than sticking your ungloved hands in Amidol or Pyrocat developer...also, the Gamblin and Graham color companies have made toxic turpentine solvent obsolete. Odorless mineral spirits and/or using linseed or walnut oil to clean brushes helps a lot for lowering toxicity.
funny thing about French Ultramarine Blue, since around late 1800's when a synthesis was discovered it has been one of the less costly blues---there was no need to grind up lapis from Afghanistan any more. It's fairly purple but still lovely. The tin and cobalt based blues are much more costly today. Enough so that I've been avoiding buying tubes of them---I can get to much the same color from phthalocyanine blue or UMB.

One of these days I'm going to learn carbon printing then extend monochrome to 4 color separations. I'm thinking an Azo yellow, quinacridone magenta and one of the Phthalocyanine blues and a carbon based black ought to be about perfect and stable for hundreds of years---better be if I'm going to work that hard to make a print.

people talk about transparent pigments---I'm not so sure the pigments are transparent so much as the particles are tiny and have such high light absorption characteristics that when dispersed they make a lot of color with little actual coverage and the transparency comes from the spaces between the pigment particles.

 

[Sirius Glass]

Magenta is not a color according to some. :devil:

What about Fuchsia and Aqua Marine? :devil:

Magenta is not a color only in the dreaded Kodachrome has been deleted thread.

 

[RobC]

Magenta is not a color only in the dreaded Kodachrome has been deleted thread.

sound like fortunately I missed that topic.

 

[Gerald C Koch]

A very pretty green pigment is paris green (copper (II) acetoarsenite). It does not discolor and at one time was used extensively on wallpaper. The problem is that it is very poisonous. It nearly did in our ambassador to Italy. For some reason the article wrongly gives the pigment as lead arsenite. The source was the leaves in the painting of roses on the ceiling which used paris green as the pigment.

http://adst.org/2013/06/more-arsenic-with-your-coffee-madam-ambassador/

 

[RobC]

a lot of artists paints had lead in them.

 

[Sirius Glass]

Magenta is not a color only in the dreaded Kodachrome has been deleted thread.

sound like fortunately I missed that topic.

It was 3,500 posts

• Calling Kodak stupid for stopping production of Kodachrome.
• Asking others to join in on making Kodachrome in someone's barn or grandma's cesspool.
• Many questions to PE demanding how to make Kodachrome at home.
• Rude comment to PE demanding that PE retract his statements that Kodachrome was too hard make or process at home.
• Threats that they were going to kidnap PE and chain him inside a barn until he made Kodachrome for them.
• A stupid self appointed expert in all things related to light, color and optics who argued with PE, others and myself that magenta is not a color.

 

[Dr Croubie]

Magenta is White minus Green. Ergo, it's got blue and red mixed together, if you look at a light spectrum it's just a bandstop filter on 500-550nm. Hence if you've got a colour enlarging head Magenta works to expose B+W paper (with its blue part) and you can put a red filter over it to focus.

But in a philosophical / etymological sense, a 'colour' is any word than can be used to describe the wavelengths of visible light that we can see. Thus 'magenta' is a colour, as is 'fuschia' (to some, to me it's a flower), even 'baby poo brown' is a colour in my dictionary.
Even White is a colour in that sense, it's just that 'white' light is made up of enough frequencies from 400-800nm (and beyond) and our eyes interpret it in a way which differs in itself (put a 3000K lightbulb next to a 6000K lightbulb and tell me they're both white). Don't get me started on the emmission spectra of the sun and absorbtion of the atmosphere...

 

[RalphLambrecht]

It seems confusing to me,calling it substantive colors when it reflects the result of mixing(adding colors)as in mixing paints:confused:

 

[RobC]

It seems confusing to me,calling it substantive colors when it reflects the result of mixing(adding colors)as in mixing paints:confused:

???

Subtractive filters(CMY) don't mix light, they start with white light and filter out certain wavelengths so they subtract colours from white light.

What is confusing is the additive filters (RGB) are called additive but they don't add, they subtract their opposites just like the subtractive filters do. The difference is that additive filters result in their own colour being the required colour which reaches the print whereas subtractive filters result in another colour (not the filter colour) being the desired colour which reaches the print.

So for B+W Blue(additive) filter results in Blue and not Green reaching the print whereas Yellow(Subtractive) results in Green reaching the print and not Blue.

[EDIT]

See Doremus reply directly below which makes the point about additive being the mixing of independant coloured light sources which I agree with. But some old enlargers which didn't have independant light sources did use RGB filters. These are pretty rare these days as the modern enlargers use Subtractive filters CMY.

 

[Doremus Scudder]

It seems confusing to me,calling it substantive colors when it reflects the result of mixing(adding colors)as in mixing paints:confused:

A typo or wrong automatic substitution or bad speech-recognition... Anyway, it should be "subtractive." Pigments, paints, etc. are called subtractive because they remove part of the white light falling on them and only reflect back the remainder. For example, a magenta (color) paint removes green from the light falling on it and reflects back the rest, which is mostly blue and red. Therefore: magenta. When you mix two paints, you end up with a paint that has the absorption characteristics of both. Yellow absorbs (subtracts) blue but has a strong green component. Blue subtracts red yellow and orange, but also has a strong green component. Mix the two together and, voilá, you get green; the only color left standing, so to speak.

Additive processes use light sources. They are called additive because the components of their spectra are combined to produce a third spectrum with all the elements of both. Red and green together make yellow. If you don't believe me, get one of those toy tops that are colored in alternating bands of red and green. Give it a good spin and, voilá, it miraculously turns yellow. The two colors hit your eye so fast it can no longer differentiate, but blends them together, additively, making yellow.

Doremus

 

[Old-N-Feeble]

Subtractive Color: You have ONE flashlight and one each magenta, cyan, and yellow filters. Turn on the flashlight. Put the magenta filter over the light output... you see a darker magenta color. Then place the cyan filter over that and you'll see even darker blue. Finally the yellow filter. If the filters are nearly perfect they will filter out ALL visible light... you see only black.

Additive Color: You have THREE flashlights and one each red, blue and green filters. Attach one filter to the light output of each flashlight. Shine the red flashlight against a white wall... you see a red spot. Now shine the green-filtered flashlight on top of the red spot... the overlapped colors create a brighter yellow spot. Turn off the green and shine the blue-filtered flashlight over the red spot... you see a brighter magenta spot. With both the red and blue flashlights still shining overlapped, add the green flashlight such that all three light spots (red, blue and green) are overlapped... if your filters are well balanced you'll see a WHITE spot.