Home › Forums › The Learning Center › Color Theory and Mixing › What is a colour, and in what sense can science measure a colour?
- This topic has 23 replies, 7 voices, and was last updated 1 year, 11 months ago by davidbriggs.
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February 19, 2020 at 11:40 pm #484231
I recently uploaded a video that may be of interest to some here. It doesn’t deal directly with painting but the questions asked pop up regularly here. The video draws on material covered on my website “The Dimensions of Colour” and in my chapter on colour spaces in the forthcoming “Routledge Handbook of Philosophy of Colour”.
“What is a Colour? Perception or Property?”
https://www.youtube.com/watch?v=4x13_k5Qgn0If you’d prefer to skim the text it’s available here:
http://www.huevaluechroma.com/118.phpColour Online (hundreds of links on colour): https://sites.google.com/site/djcbriggs/colour-online
The Dimensions of Colour: www.huevaluechroma.com
Colour Society of Australia: www.coloursociety.org.auNovember 28, 2020 at 3:59 am #1358605Test reply.
Doug
We must leave our mark on this worldNovember 28, 2020 at 4:38 am #1358613Thanks David – great video – looking forward to the next.
November 30, 2020 at 11:04 pm #1359601Thanks, Norman.
The second video in the series is called “Hue and it’s Components”
Colour Online (hundreds of links on colour): https://sites.google.com/site/djcbriggs/colour-online
The Dimensions of Colour: www.huevaluechroma.com
Colour Society of Australia: www.coloursociety.org.auDecember 3, 2020 at 5:23 am #1360293Thanks again David – really clear! It’s very helpful when mixing paints to have these concepts in the background – it can give confidence using what might otherwise seem weird accidents (for example – mix a (correct) violet and slowly add a yellow – amazingly & usefully it neutralises to a dark grey or black). It can also help to just accept the way the psychophysical system works & set aside the (in my opinion) often fruitless arguments about definitions of primary, secondary & complementary colours & concentrate on the business of practical paint mixing (I do find the concept of a mixing complement useful though). Another video from you about paint mixing would be welcome if you have time!
December 11, 2020 at 3:40 am #1362824David – I realise that I don’t really see why mixing magenta & ultramarine & yellow gives me a good black:
Mixing ultramarine and magenta I get a very dark violet or purple. I get this as reflectance curves for these pigments show that magenta lets through some blue light and a lot of red light, and ultramarine lets through some red and a lot of blue light – so subtractive mixing gives only a little blue light and a little red light but almost nothing between. Adding white paint to the mix gives a paler version of red & blue light only.
However – according to http://www.huevaluechroma.com/045.php, yellow pigments really just stop blue & allow the rest. If this is so surely when I add yellow paint to my violet mix I should get red? If yellow pigments stopped red & blue and allowed yellow or mid-wavelengths I can see that black would result.
December 13, 2020 at 11:13 pm #1363616I can show you an indication of what might be happening with your paints from the modelling of the hansa yellow, quinacridone magenta and ultramarine mixture shown in the attachment. All three paints reflect some long (red) wavelengths, so how can we get a neutral mixture? A: By adjusting the proportions of the three paints until the small amount of light reflected by the mixture is achromatic. The spectral reflectance (upper left) of the mixture includes a very small amount of orange-red wavelengths balanced by a very small amount of light around the complementary cyan-blue (remember the very longest wavelengths have very little effect visually). According to the model this small amount of achromatic reflected light is enough to give this mixture a Munsell value just above 2.
Colour Online (hundreds of links on colour): https://sites.google.com/site/djcbriggs/colour-online
The Dimensions of Colour: www.huevaluechroma.com
Colour Society of Australia: www.coloursociety.org.auDecember 14, 2020 at 12:48 am #1363622Good stuff as always David – thanks. Your explanations about the visually-complementary spectral bumps being able to balance each other to make neutral greys is what I always assumed.
Why does Ultramarine Blue plot so close to neutral in the mixing plot…is that its masstone color? Also interesting how the mixing paths are very much not straight lines (as I think a lot of people, including myself, tend to assume).
December 14, 2020 at 6:06 am #1363678Thanks very much Patrick. Yes, it would be a mass tone. The reading for ultramarine in that brand is also very low in value (1.4), so it’s probably about as high in chroma as you can get at that value. Some other acrylic brands have higher value and chroma readings – maybe they have “milkier” acrylic binders.
It’s definitely not a good idea to picture those mixing paths as straight. For example the curve towards green of mixtures of yellow and blue paints is very consistent.
Colour Online (hundreds of links on colour): https://sites.google.com/site/djcbriggs/colour-online
The Dimensions of Colour: www.huevaluechroma.com
Colour Society of Australia: www.coloursociety.org.auDecember 14, 2020 at 11:35 am #1363786A question if you don’t mind..
I know of quite a few mixes that can make a deep transparent black (and some that are lighter but more opaque).
But I haven’t seen any mixes that are any darker than the deepest carbon black.
PBk1 Analine black is darker when matte than other matte acrylics/oils. But when varnished it actually seems to becomes lighter and the carbon blacks darken to the same value.
Are you aware of any mixes to make a value deeper than PBK6/7, or is this the darkest that can be made (in available paints – not including Vantablack or other carbon nanotube style paints)
December 14, 2020 at 7:04 pm #1363894Sorry, I don’t know of any that are definitely darker. I’d recommend Graydon Parrish as someone who is much more interested than I am in which pigments and brands take you to the extreme outer limits of the artists’ paint gamut. You can contact him via his Facebook Group. I have an idea he once said that Prussian Blue in a particular brand had the lowest value he had encountered, but best check with him.
Colour Online (hundreds of links on colour): https://sites.google.com/site/djcbriggs/colour-online
The Dimensions of Colour: www.huevaluechroma.com
Colour Society of Australia: www.coloursociety.org.auDecember 15, 2020 at 11:03 am #1364064No problem, it’s not an easy question. Thank you for your help
December 15, 2020 at 2:01 pm #1364096Richard, don’t know if this will help…you might’ve seen this on handprint:
“Aniline black PBk1 is an impermanent azine pigment, available from about 6 pigment manufacturers worldwide. Holbein peach black, the only commercial source, contains the pigment in mixture with carbon black, which must be the dominant ingredient as the paint is quite lightfast; it produces subtle and active textural effects wet in wet, and has the darkest masstone value of any black paint. Because of the azine pigment, this paint should perhaps not be used in tints or diluted.”
And…
“However, if a potent, achromatic dark gray is the goal, then it is more efficient to use two mixing complements. The darkest and most efficient mixture along the red/green contrast consists of perylene maroon (PR179) and phthalocyanine green BS (PG7), roughly in the proportions 5:1; along the orange/blue contrast the darkest mixture is quinacridone orange (PO48) and iron blue (PB27) in roughly 4:1 proportions. (Exact recipes depend on paint brands; alternative mixtures are listed in the page on watercolor mixing complements.) Daniel Smith, M. Graham, and Da Vinci offer all four paints; Winsor & Newton, Rowney Artists and MaimeriBlu make a quinacridone maroon (PR206) that you can substitute for the perylene maroon and quinacridone orange.
In the correct proportions, either the three paint or two paint mixtures give an extremely dark, dead on black color; tweaking the proportions of the paints will shift the hue to mimic any commercial dark shade paint (sepia, perylene black, indigo, neutral tint, payne’s gray), as well as dark shades that are magenta, turquoise or deep yellow. In masstone applications these mixtures are actually darker valued than most lamp or ivory blacks (PBk9). They create a velvety luster, rather than the usual carbon black dullness, that harmonizes well with other dark valued paints; they can be used to produce shades of any paint, and when applied wet in wet or used in diluted glazes, color separation among the pigments will produce subtle and shimmering color effects.”
More about Perylene Maroon:
“Its mixing complements include phthalo green BS (PG7), which produces a pure jet black darker than most carbon pigment paints, and perylene maroon stains tenaciously, again like alizarin crimson. See also the section on perylene pigments.”
W&N Perylene Green (watercolors) :
“In concentrated form the paint produces a very dark near neutral hue, almost indistinguishable from a true black, with a relatively small drying shift; mixed with an unadulterated dioxazine violet, quinacridone violet or perylene violet (PV29) it creates a darker and more stable black than most carbon based paints. (Note that additives used to adulterate these expensive pigments or adjust the vehicle may cause an unexpected whitening of the dried color. If you don’t get a deep black, try another brand of paints.)”
December 16, 2020 at 1:23 pm #1364367Thanks Patrick.
I have seen this on Handprint. However the difficulty here is that watercolour is a matte medium and I have found that carbon/mars black pigments are lighter in value when dry there but darken considerably when in a gloss medium or when glossy varnish is applied over the top.
So I think it’s perfectly accurate that for matte colours a mix can have a lower value than a traditional black, but I haven’t found this the case when the surface is glossy.
December 17, 2020 at 5:34 am #1364528Thanks David for your reply (Dec 13th) – and supplying the really key piece of information (that although there is some orange-red left over – with the right mixture the total reflected light appears neutral to the eye as there is also an amount of cyan – and very dark as the overall amount of light reflected is very small).
Can I ask what software you used there please? Is is generally available?
The following discussion about blacks is really interesting – and reinforces to me the idea that one needs to choose ones paints carefully (after a lot of experimentation – and probably money wasted on tubes that aren’t used in the end) so that one can make all the colours that one needs – and stick with them to be able to use them quickly & reliably. So this means staying with not just a pigment type but an actual manufacturer’s paint type.
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