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Why does azure make a better cyan than teal for color mixing?

On the HSV spectrum, cyan sits at 180 degrees, which is bright teal, whereas most printer inks and best primary blues for painting and sketching seem to sit between 190 and 205 degrees on HSV.

If teal is literally cyan, and azure is not quite cyan, shouldn't it make a better cyan than azure since it absorbs red more purely than azure does (and therefore allow finer control in subtractive color mixing)?

Azure seems so popular for cyan that the "new color theory" painters on youtube seem to almost always point to an azure: cerulean (often called brilliant blue), phthalo blue, or prussian blue when they refer to cyan, none of which are really "cyan" in my eyes.

Why does azure seem so much better at mixing than teal (a true shade of cyan)?

Azure Teal

  • I agree that it is strange that the CMY colors aren't distributed evenly in the color circle. I haven't been able to find an explanation, but I guess the short answer is: It's complicated! In printing and painting you can't just play around freely with wavelengths of light. You are very limited by the medium, the tools and the chemical attributes (and availability) of the inks. Lots of nonlinear stuff going on. I guess the CMY colors are just the best compromise when everything is taken into account. – Wolff Aug 16 '18 at 20:14
  • I'm curious if any particular factor has a particularly large influence this decision. – Dmitry Aug 16 '18 at 20:18
  • What do you mean by better for colour mixing? 4C process printing is not "mixing" colours. – Stan Aug 18 '18 at 2:35
  • The biggest factor in the decision is that the chosen primaries work together in a predetermined, consistent, reliable, and economic manner to produce a very good rendition of a colour image. – Stan Aug 18 '18 at 2:49
  • It doesn't matter what your definition of "better" is so long as it works with the rest of the "set" of process colours. So far, cyan "plays nice" with its friends magenta, and yellow. most of the time. – Stan Aug 18 '18 at 2:53
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The hsv color space does not actually reflect physics and neurological truth of how the system works. So the spread of values is more artistic/practical consideration than scientifically motivated. So doing any reasoning on color properties by the angle in HSV space is just plain misleading.

Second color names are also pretty arbitrary. And mean different things to different users. The names don't necessarily also follow the same angle throughout the lightness spectrum. Neither is the spread of colors in the wheel especially well motivated, i would spread it out a bit differently to be honest. Or then use some CIE derived space in polar form.

Lets face it artists in the loop systems can easily mix the colors out of nearly any combination of base colors. Just that techniocal systems that need to work predictably even without human intervention can not.

Third not all printers have the came cyan color as their base.

Ammendum: Theres nothing simple about human vision. it is far far more complicated that most people assume, and brief introductions lead you to believe.

  • i was only using hsv to identify the color rather than reasoning about them. While names of colors are arbitrary, the wavelengths of red green and blue and their complementaries are reasonably consistent. Why is teal a less popular option for a primary than azure? – Dmitry Aug 16 '18 at 8:23
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    @Dmitry Not really, human vision is highly nonlinear and if you look at a standard observer graph youll notice that the difference in wavelengths between green red is way different from blue green. Also what human condiers to be in between is noweher near that simple as taking the color in between. Hell, motivating things with wavelegths wont even begin to explain magenta. – joojaa Aug 16 '18 at 8:27
  • I love your invention of a word for edited additions as a cross between "addendum" (added content) and "amend" (make better). Ammendum: great neologism (new word). I look forward to your posts. – Stan Aug 18 '18 at 2:59
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Very good question; the answer has mainly to do with the fact that we must choose from actual available pigments, not hues. There just isn't any cheap, highly chromatic, permanent transparent pigment of the hue you're calling cyan that compares with phthalocyanine blue, the various varieties of which are in the hue range you're calling azure. One kind of cobalt green can be close to digital cyan but it is expensive and toxic and more to the point opaque, which restricts the range of colours it can yield. Another relevant factor is that because mixing paths between blue and yellow pigments consistently veer out towards green, the non-ideal hue of phthalocyanine blue is not as much of a drawback as it would be otherwise. http://www.huevaluechroma.com/pics/0.2.6.jpg

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HSV is a way to describe RGB colours. It has little to do with physical paints, inks and pigments.

What do you mean by cyan? Are you talking about the bright blue #00FFFF in RGB?

enter image description here

If so, then the answer is that paint and inks use different primaries because they work using a different colour system called subtractive colour. By contrast, RGB is a colour model that's additive. The bright RGB blue #00ffff is not available in paints/inks because it's out of gamut in subtractive colour models. You should probaby google "additive versus subtractive colour" for more in depth information.

  • I'm aware of additive vs subtractive. In the original post, i intentionally darkened my cyan in the post to a shade in the gamut under common brightness. shouldn't a dark cyan still mix better than a darker azure? or is azure inherently brighter than teal? – Dmitry Aug 16 '18 at 16:37
  • @Dmitry to be honest I don't really know what you mean by azure and teal, as far as I am concerned the colours you posted look to me like a darker cyan and turquoise (on the right). These aren't precise colours, and colour names are rather arbitrary. Also neither of these quite match process cyan, which is used in CMYK printing. – Billy Kerr Aug 16 '18 at 17:31
  • process cyan is at 196 hsv,; the blue i showed was 193 hsv, and cyan was 180 hsv. the blue and cyan i showed are both slightly darkened to be more comparable, in reality the azure is brighter than cyan since cyan as bright as azure would be out of gamut possible on paper with transparent medium. Process cyan is closer to the blue I showed than the cyan I showed. Does the difference in brightness alone make azure mix better than darker cyan? – Dmitry Aug 17 '18 at 0:31
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    @Dmitry 4C process colour is not, and was not intended to be perfect solution to colour image reproduction. It is a practical system developed in stages over years of gradual technological improvements. Wanted colours outside the 4C process colour gamut require different treatment. This is where "spot" colours are used to supplement the limited subtractive gamut. – Stan Aug 18 '18 at 2:49

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