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I'm not sure which test image you're talking about. This one seems to have low-contrast detail everywhere in the data range: https://1.bp.blogspot.com/-H-1I69V

by Zarel 7y ago

I'm not sure which test image you're talking about. This one seems to have low-contrast detail everywhere in the data range: https://1.bp.blogspot.com/-H-1I69V29VM/XVWeDrO7EPI/AAAAAAAAEdI/rc4kcJYaiNkTgazt-P1tJ7xCgeXBTuNFgCLcBGAs/s1600/image31.png https://1.bp.blogspot.com/-H-1I69V29VM/XVWeDrO7EPI/AAAAAAAAE... https://1.bp.blogspot.com/-6zVTINtwP60/XVWeKMWavuI/AAAAAAAAEdM/VYew83Y03bI37wZDCXmqYaduNbLWAbSawCLcBGAs/s1600/image22.png https://1.bp.blogspot.com/-6zVTINtwP60/XVWeKMWavuI/AAAAAAAAE... While it's true that Turbo/Jet have low lightness contrast in the middle range, it makes up for it with hue contrast. While there are of course ways to improve contrast in specific parts of a data range, I like Turbo for having high contrast in general, to make it less necessary to "zoom in" on a specific range, and also to have even higher contrast after zooming in.

jacobolus 7y ago
Hue contrast is not very salient to the human visual system. But while we’re at it there’s also not very much hue contrast in the middle of this color scheme. It goes from light bluish green to light yellowish green. Yes that cherry-picked image. Their original data is some kind of (log-scaled?) distance map, where half (?) of the image is in the bottom 20% of the data range. They put a bunch of apparently important data between values of like 0.00 and 0.05, but don’t have any substantial amount of important data between 0.45 and 0.55. Their color scheme has very strong lightness contrast in the 0.0 to 0.05 range, and almost no lightness contrast in the 0.45 to 0.55 range. If they had instead put a bunch of important low-contrast detail in the mid range, it would become nearly invisible compared to the old scheme. If you really care about the data from 0.0 to 0.05, and don’t really care about the data from 0.45 to 0.55 you can apply some function (e.g. a power function, or inverse smoothstep or something) to your data beforehand.
- rocqua 7y ago
  > They put a bunch of apparently important data between values of like 0.00 and 0.05, but don’t have any substantial amount of important data between 0.45 and 0.55. I don't think they chose the image to best present their colormap. It seems more likely that they designed their colormap to work well for a few images, including this image. Call it a very weak form of Hanlon's Razor
- Zarel 7y ago
  Don't have any substantial amount of important data between 0.45 and 0.55? The biggest tree is in that range! How is that not low-contrast detail in the mid-range? https://1.bp.blogspot.com/-H-1I69V29VM/XVWeDrO7EPI/AAAAAAAAEdI/rc4kcJYaiNkTgazt-P1tJ7xCgeXBTuNFgCLcBGAs/s1600/image31.png https://1.bp.blogspot.com/-H-1I69V29VM/XVWeDrO7EPI/AAAAAAAAE... https://1.bp.blogspot.com/-6zVTINtwP60/XVWeKMWavuI/AAAAAAAAEdM/VYew83Y03bI37wZDCXmqYaduNbLWAbSawCLcBGAs/s1600/image22.png https://1.bp.blogspot.com/-6zVTINtwP60/XVWeKMWavuI/AAAAAAAAE... Look at the images again. 0.45 to 0.55 is green. Do the leaves on the front of the closest tree actually look harder to distinguish in Turbo than in Inferno? It doesn't matter which function you apply to your data beforehand, it won't change that Turbo has more distinguishable steps than Viridis/Inferno. Turbo goes red-yellow-green-blue-black, Viridis goes yellow-green-black. Of course Turbo will be able to show more contrast.

by Zarel 7y ago

jacobolus 7y ago

Hue contrast is not very salient to the human visual system. But while we’re at it there’s also not very much hue contrast in the middle of this color scheme. It goes from light bluish green to light yellowish green. Yes that cherry-picked image. Their original data is some kind of (log-scaled?) distance map, where half (?) of the image is in the bottom 20% of the data range. They put a bunch of apparently important data between values of like 0.00 and 0.05, but don’t have any substantial amount of important data between 0.45 and 0.55. Their color scheme has very strong lightness contrast in the 0.0 to 0.05 range, and almost no lightness contrast in the 0.45 to 0.55 range. If they had instead put a bunch of important low-contrast detail in the mid range, it would become nearly invisible compared to the old scheme. If you really care about the data from 0.0 to 0.05, and don’t really care about the data from 0.45 to 0.55 you can apply some function (e.g. a power function, or inverse smoothstep or something) to your data beforehand.

rocqua 7y ago
> They put a bunch of apparently important data between values of like 0.00 and 0.05, but don’t have any substantial amount of important data between 0.45 and 0.55. I don't think they chose the image to best present their colormap. It seems more likely that they designed their colormap to work well for a few images, including this image. Call it a very weak form of Hanlon's Razor
Zarel 7y ago
Don't have any substantial amount of important data between 0.45 and 0.55? The biggest tree is in that range! How is that not low-contrast detail in the mid-range? https://1.bp.blogspot.com/-H-1I69V29VM/XVWeDrO7EPI/AAAAAAAAEdI/rc4kcJYaiNkTgazt-P1tJ7xCgeXBTuNFgCLcBGAs/s1600/image31.png https://1.bp.blogspot.com/-H-1I69V29VM/XVWeDrO7EPI/AAAAAAAAE... https://1.bp.blogspot.com/-6zVTINtwP60/XVWeKMWavuI/AAAAAAAAEdM/VYew83Y03bI37wZDCXmqYaduNbLWAbSawCLcBGAs/s1600/image22.png https://1.bp.blogspot.com/-6zVTINtwP60/XVWeKMWavuI/AAAAAAAAE... Look at the images again. 0.45 to 0.55 is green. Do the leaves on the front of the closest tree actually look harder to distinguish in Turbo than in Inferno? It doesn't matter which function you apply to your data beforehand, it won't change that Turbo has more distinguishable steps than Viridis/Inferno. Turbo goes red-yellow-green-blue-black, Viridis goes yellow-green-black. Of course Turbo will be able to show more contrast.