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Colour Maps with Uniform Perceptual Contrast

Western Australia

Bad colour maps can hide big features and create false anomalies.

Many colour maps provided by vendors have highly uneven perceptual contrast. Colour maps may have points of locally high colour contrast leading to the perception of false anomalies in your data when there is none. Conversely colour maps may also have 'flat spots' of low perceptual contrast that prevent you from seeing features in the data.

The colour maps shown here are rendered on a test image consisting of a sine wave superimposed on a ramp function. The sine wave amplitude is set so that the range from peak to trough represents a series of features that are 10% of the total data range. The amplitude of the sine wave is modulated from its full value at the top of the image to zero at the bottom.

In evaluating a colour map we want to see the sine wave pattern uniformly visible across the image from left to right.  At the very bottom of the image, where the sine wave amplitude is zero, we just have a linear ramp which simply reproduces the colour map. Given that the underlying data is a featureless ramp we should not perceive any identifiable features across the bottom of the image.

We have developed a set of design techniques that ensure colour maps have uniform perceptual contrast across their full range. We believe these colour maps will allow more reliable and consistent interpretations of data. You can download these colour maps and find more details about them using the following links. ​