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IBM did research back in the 90s on perceptually-based colormaps and how to best represent various types of data within the color dimensions of luminescence, sa

IBM did research back in the 90s on perceptually-based colormaps and how to best represent various types of data within the color dimensions of luminescence, saturation and hue [1]. For exmpale, they found that, (1) Hue was not a good dimension for encoding magnitude information, i.e. rainbow color maps are bad. (2) The mechanisms in human vision responsible for high spatial frequency information processing are luminance channels. If the data to be represented have high spatial frequency, use a colormap which has a strong luminance variation across the data range. (3) For interval and ratio data, both luminance- and saturation-varying colormaps should produce the effect of having equal steps in data value correspond to equal perceptual steps, but the first will be most effective for high spatial frequency data variations and the second will be most effective for low spatial frequency variations. === [1] https://www.research.ibm.com/people/l/lloydt/color/color.HTM https://www.research.ibm.com/people/l/lloydt/color/color.HTM or as pdf: https://github.com/frankMilde/interesting-reads/blob/master/ibm-research__why-should-engineers-and-scientists-be-worried-about-color.pdf https://github.com/frankMilde/interesting-reads/blob/master/...

swimfar 6y ago
"rainbow color maps are bad" I disagree with blanket statements like this. Rainbow color maps aren't ideal for showing relative difference in values. But they are great if you want to be able to tell what the value (range) in a given location is. This is almost impossible with a 10-shade grey-scale legend or a height map. Disclaimer: I use rainbow color maps all the time because I'm often interested in critical value areas of my plots.
- username90 6y ago
  Color blind people likely wont be able to read your rainbow plots though. For example, for me Jet is just Blue - White - Green - Dark Green, with white being left of the middle. (Blue + Green is white since I don't see red) So for me reading a Jet plot is basically impossible, they just doesn't make sense. Like, if a value is weak it is the brightest white, then if it gets even lower it gets blue. It peaks at green in the middle and then goes darker and darker as it gets stronger. Totally unintuitive. Edit: Even worse is that how I see it depends strongly on what medium you use for the red and green channels. On some screens/paints red is basically black while others are almost fully green, depending on exactly where in the spectrum it is.

swimfar 6y ago

"rainbow color maps are bad" I disagree with blanket statements like this. Rainbow color maps aren't ideal for showing relative difference in values. But they are great if you want to be able to tell what the value (range) in a given location is. This is almost impossible with a 10-shade grey-scale legend or a height map. Disclaimer: I use rainbow color maps all the time because I'm often interested in critical value areas of my plots.

username90 6y ago
Color blind people likely wont be able to read your rainbow plots though. For example, for me Jet is just Blue - White - Green - Dark Green, with white being left of the middle. (Blue + Green is white since I don't see red) So for me reading a Jet plot is basically impossible, they just doesn't make sense. Like, if a value is weak it is the brightest white, then if it gets even lower it gets blue. It peaks at green in the middle and then goes darker and darker as it gets stronger. Totally unintuitive. Edit: Even worse is that how I see it depends strongly on what medium you use for the red and green channels. On some screens/paints red is basically black while others are almost fully green, depending on exactly where in the spectrum it is.