Which model is right when considering Color Gamut ?


Well-known member
I have been learning about Color Management and this Color Gamut thing has confused me a bit . Which shape is right - the horse shoe or the round color wheel type. (Please refer the linked images)


If its horse shoe, Where does it come from ?
The horseshoe shape is a 2D slice through a 3D representation of gamut. There's a movie of the 3D gamut here with the horseshoe at its base: http://the-print-guide.blogspot.ca/2009/03/am-and-fm-gamuts-compared.html


Well-known member
For printing processes, gamut is usually represented as a three dimensional volume in CIELAB space. RGB monitors often have their gamut represented as a triangle on the xy plane (with the horseshoe shape) since they can be simply described that way.

The horseshoe shape is usually seen on a two dimensional xy planar slice of the xyY space. It can be thought of as an overlay of possible colors onto the xy graph. While you can reference x=.9,y=.9 on that plane, you would be describing an imaginary color, not an actual possible color in the real world. The purest, most chromatic colors you can possibly get are pure narrow wavelengths of light, therefore the colors you get from them define the boundary of real colors. The horseshoe shape is derived by plotting all of the pure wavelengths onto the graph. When you're plotting arbitrary data, it is essentially a visual aid to show the bounds of real-world possibility.

I don't believe any sort of "wheel" is commonly used to represent gamut. For a printing process, the gamut probably can't be accurately represented with any two dimensional model.

Correct Color

Well-known member
Which shape is right - the horse shoe or the round color wheel type. (Please refer the linked images)
Well, the answer is that neither is 'right' and neither is 'wrong.'

They're both just representations and if either one allows you to visualize what's actually happening, then it has worked for your needs.

And what's actually happening is that in a given condition, and device that reproduces color with primaries will only be able to reproduce certain colors. Those colors are that device's gamut, in that condition. There are myriad ways to represent that, and in fact, both the methods you've shown are a little limited in that they're only two dimensional; but again, that doesn't make them necessarily right or wrong, it just makes them what they are.

Mike Adams
Correct Color

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