Color wave length and hue

Is there any method to get color hue from its wave length?

Answer 1

[Walter Roberson]

Hue = (650 - wavelength)*240/(650-475);

Extracted from: http://www.physics.uoguelph.ca/applets/Intro_physics/refraction/LightRefract.java

Note: the denominator consists of two seemingly arbitrary limits in the code. The 240 refers to the maximum hue value of 240 that is used in standard 8 bit Hue representation.

Visible light is about 400 to 700 nm, with 650 nm being the frequency of red. 475 is blue. Both indigo and violet fall below this limit, but the CIE model that defines the theoretical map of wavelength to hue has to treat colors in that range separately, and it could be that 475 nm is the effective limit for standard Hue calculation, perhaps requiring negative Hue (yes, that is possible in color theory, but not in standard 8 bit Hue representation.)

[Subhadeep Koley]

Sir, why did you subtract the wavelength from 650 precisely? Is there any logic?

[Walter Roberson]

Sorry, I do not know, I did not write the code I linked to. I suspect the hue calculation given in that code might only be valid for colors in the range of red to blue, and that beyond that might start needing a different formula. The HSV and L*a*b* calculations are conditional based upon which component is strongest, and so calculating hue might get a bit complicated outside the noted range.

[Nikhil R.]

Just a disclamer: I tried 400º wavelength, but got 342º hue, when I was expecting ~280º. I think something is wrong with the formula.

Answer 2

[Nikhil R.]

Hi! So, I have a formula from stackoverflow.com; if h = hueº, and w = wavelength nm.

w = (400 / 270)h. You use this as a graph:

Or: Desmos Automatic Calculator

Edit: Note: This formula tries to get the closest possible to the same. Hue tends to be brighter as for example:

400nm/~270º

~265nm/~180º

~575nm/~390º

...

Table of official hues to wavelengths (Approximently):

Name Hue Wavelength

Red 0/360 650

Orange 45 600

Yellow 60 420

Lime 100 575

Cyan 180 475

Purple 270 400