Hue, saturation and brightness

All the colours you can see on your screen can be described by three parameters: hue, saturation and brightness.

Hue

The table below shows the way your computer equipment describes hue, at saturation = 100% and brightness = 100%.;

This table gives a rough idea of how hue angle works, but you have to remember that your screen is an additive-colour medium, whereas paint is a subtractive medium. Visual perception models for pigment-based colour will work on a slightly different  basis; for example, in the CIElab model the zero hue angle is yellow, not red.

Saturation and brightness

I always find it difficult to imagine how decreasing the saturation and brightness of a colour affects its appearance – hence I have made this table. Again, this is a computer-based model, but this is all the equipment that I (and probably you) have available. I chose orange (hue angle = 30°) as we have more words (e.g. brown, tan, fawn, ochre, beige, tawny, buff, chestnut, elephant) to describe these tints, shades and tones than for any other hue. Computer screens are not very good at representing bright orange, so everything is a bit subdued.

You will see that tints (equivalent to pigment + white) give you a gradient of decreasing saturation, at full brightness.  Shades (equivalent to pigment + black) give you a row of increasing darkness at full saturation. The middle block of greyed orange cells, labelled with the ¤ symbol, approach natural colours. In some nomenclatures they are referred to as (equivalent to pigment + black) give you a row of increasing darkness at full saturation. The middle block of greyed orange cells, labelled with the ¤ symbol, approach natural colours. In some nomenclatures they are referred to as tones, but this may be confusing as "tone" can also mean brightness. Life is never easy.

If you find all this a bit over the top, the diagram below should simplify things.

On the other hand, if this has whetted your appetite, there's an enormous amount of info here: http://www.handprint.com/HP/WCL/water.html. This site is concerned mainly with watercolour, but has exhaustive and accessible articles on colour theory.

End of article. 15 Dec 2006.

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