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> rainbow palette for use in my data visualisations. Indeed for her kind of data the rainbow palette works okay. But if you have to visualize more complex / de
by splittingTimes 4y ago
> rainbow palette for use in my data visualisations.
Indeed for her kind of data the rainbow palette works okay. But if you have to visualize more complex / denser data, beware of the pitfalls of the rainbow color palette. It is not always the best choice.
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 example, 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 color map which has a strong luminance variation across the data range.
(3) For interval and ratio data, both luminance- and saturation-varying color maps 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.
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[1] the original link got removed from IBMs website. Back in the day it was under
https://www.research.ibm.com/people/l/lloydt/color/color.HTM https://www.research.ibm.com/people/l/lloydt/color/color.HTM
A pdf copy is here:
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/...
- ajuc 4y agoWhat's wrong with grayscale? Why do we need to add confounding variables?
- WastingMyTime89 4y agoPointing that luminance is the best channel to encode spatial frequency is akin to encouraging greyscale. It’s just that you can do it with a hue and a non zero saturation if it suits the style you are looking for. Plus sometimes you have more than on me set of data mixed and it’s useful to be able to distinguish both by using multiple colours.
- visarga 4y agoWhen you want to plot a categorical distribution you need to encode category by colour, but you want them to appear maximally distinctive.
- nerdponx 4y agoA whole lot of work has been done more recently on "perceptually uniform" color palettes. See the Brewer color palette family, the "scientific colourmaps" by Crameri, and the Viridis color palette family, the latter of which was famously adopted by Matplotlib several years ago.
- p-e-w 4y agoNote that most modern palettes are designed with various forms of color blindness in mind. For that purpose, they artificially restrict the range of colors, which in turn reduces the visual information they can carry for the vast majority of people who have normal color vision. I'd be super interested to see a study that examines how color blindness-aware design affects people without color blindness. Such design often completely avoids red hues, which are of huge importance as visual cues to normally sighted people. It's hard to imagine this doesn't have a negative impact somehow, yet I've never seen this discussed anywhere.
- realgeniushere 4y ago
- touch_abs 4y ago
- ScottEvtuch 4y agoAren't something like 1 in 20 or so people color blind? I'd hardly consider that as an edge case. That's roughly the odds of being over 6ft tall in the US.
- tygrak 4y agoYou might not know this based on your response, but almost 10% of men are colorblind.
- nerdponx 4y agoThis is ignorant and wrong. You are assuming that colorblind-friendly palettes are worse than others, but that isn't the case. In my experience, colorblind-friendly palettes actually tend to be nicer looking. It's not wrongthink, but you might just be a jerk.
- twelvechairs 4y ago> (1) Hue was not a good dimension for encoding magnitude information, i.e. rainbow color maps are bad. Your inference doesnt follow from the first point. Hue is bad for magnitude because you dont see a different hue as 'more' or 'less' just 'different'. Hue is great for representing difference without defining one as a focus or preference over the other.
- ilyt 4y ago>Indeed for her kind of data the rainbow palette works okay. But if you have to visualize more complex / denser data, beware of the pitfalls of the rainbow color palette. It is not always the best choice. There is already a trap in this palette, the first color looks awfully like the last. It's fine if you just want a palette for a bunch of lines but using it for heatmap could be a bit misleading in edge cases
- IIAOPSW 4y agoI have a pet theory that certain high spatial frequencies bleed into being perceived a colors anyway. The reason being that the red, green, and blue cones in the retina each have a different amount of space between them but are otherwise organized in the same pattern. Thus if the brain sees something with the same spacing as the blue cones, its going to assume that's caused by it being a blue object (rather than a black/white object which happened to have the same spatial freq as the blue cells). You seem to know the literature here, is there anything validating or invalidating my pet theory?
- photoGrant 4y agoThis is called metameric failure
- hunter2_ 4y agoI'm no expert, but that sounds a lot like how halftone and dithering work.
- nyanpasu64 4y agoI've never noticed such happening by eyes, but I've definitely seen distant ocean reflections (tiny randomly-shifting specks of light) being misinterpreted as colors by Bayer matrix camera sensors.
- IIAOPSW 4y agofull disclosure, this pet theory is entirely based on observations of people on LSD. High frequency spatial patterns consistently get distorted in colorful ways.
- azalemeth 4y agoThis is a whole area of research (as you probably know). I personally only like HSV colourmaps for visualisations of phase, as it has no boundaries at the edges and therefore when you wrap over 2π again you don't get a hard discontinuity. Often you're not actually interested in what the "number" is, but how quickly it is cycling – something that it gets across quite well.
- sj4nz 4y agoI agree that trying to use hue for encoding magnatude information is not great, but man, how many times have I given up on someone's infographic that decided to use four different shades of blue and purple you can't tell apart when the markers are only eight or sixteen pixels on the screen. I should hope the 12-bit rainbow palette would be adopted for those kinds of visualizations.
- nine_k 4y agoWhat is often needed in visualizations is showing several parameters next to each other. Think not color maps that showvariation of one value, like a heat map, but line or bar charts, or area maps with various pars marked.