4 ms·

If your data is centered around zero (i.e. lots of uninteresting data points near zero), why would you want your perceptual peak there? I can't think of any div

by blix 6y ago

If your data is centered around zero (i.e. lots of uninteresting data points near zero), why would you want your perceptual peak there? I can't think of any divergent colormap that has this feature. In jet the cyan and yellow regions highlight small deviations from zero, which are usually more interesting than zero itself. I understand that jet is poor for accessiblity, and I don't use it for that reason, but in my experience jet is used frequently for divergent data and highlighting extreme values. The article's argument for perceptually uniform colormaps in this context is weak to non-existent. Surely roma wouldn't look very good on a photo of Curie.

nemetroid 6y ago
Why is perceptual uniformity (in each direction) less important for diverging colour maps? Used as a diverging map with zero at green, jet ramps up in intensity up to yellow/cyan, and then ramps down again. As a result it draws attention to mildly deviating areas.
- blix 6y ago
  It is still important, and jet certainly has major flaws. I just think it's not so useful to compare jet to non-divergent colormaps. Any divergent colormap would look bad on a photograph of a human, which seems to be the main evidence provided in this paper. In a deleted reply to my comment, a user referenced a paper by Borkin [1], that actually compares the quality of decisions made using jet vs other divergent colormaps. Jet loses. It's a shame this sort of argument wasn't included in the ncomms article, because imo it would do a much better job of convincing people who like jet. [1] https://www.eecs.harvard.edu/~kgajos/papers/2011/borkin11-infoviz.pdf https://www.eecs.harvard.edu/~kgajos/papers/2011/borkin11-in...
  - nemetroid 6y ago
    > I just think it's not so useful to compare jet to non-divergent colormaps. I agree, in the "this should be so obvious that it doesn't need an article written about it" sense. But the continued prevalence of jet used as a sequential colour map suggests that the comparison is necessary.
  - rozab 6y ago
    I think the reason the example with the photo is useful is because it shows how the colourmap creates features where none exist in the data (due to the nonlinear gradient). When looking at the photo with Jet I can see discrete areas of flat colour, like the Obama 'Hope' poster, but really these boundaries are just artifacts of the colourmap. I think the same thing happens in the arteries example in that SciPy talk. Sure it could be useful in some scenarios to highlight specific parts of the spectrum (like you mentioned with small deviations from the zero point) but at the end of the day the colourmap doesn't know anything about the data and shouldn't make any assumptions. Highlighting certain small intervals in the data could be better achieved with preprocessing, i.e. some polynomial scaling function.
    - blix 6y ago
      If you look at the photo of Curie using any divergent colormap, you get roughly the same effect. The problem is that the colormap is divergent and replaces white with a dark color, not anything intrinsic to jet. If you map this image with BWR or roma you end up with similarly unappealing results. IMO roma is actually the worst of the bunch, despite being the most 'scientific.' Whoever decided that deep, saturated blue and dull brown-red are equally distinct from beige needs to reevalute their model of color perception.

by blix 6y ago

nemetroid 6y ago

Why is perceptual uniformity (in each direction) less important for diverging colour maps? Used as a diverging map with zero at green, jet ramps up in intensity up to yellow/cyan, and then ramps down again. As a result it draws attention to mildly deviating areas.

blix 6y ago
It is still important, and jet certainly has major flaws. I just think it's not so useful to compare jet to non-divergent colormaps. Any divergent colormap would look bad on a photograph of a human, which seems to be the main evidence provided in this paper. In a deleted reply to my comment, a user referenced a paper by Borkin [1], that actually compares the quality of decisions made using jet vs other divergent colormaps. Jet loses. It's a shame this sort of argument wasn't included in the ncomms article, because imo it would do a much better job of convincing people who like jet. [1] https://www.eecs.harvard.edu/~kgajos/papers/2011/borkin11-infoviz.pdf https://www.eecs.harvard.edu/~kgajos/papers/2011/borkin11-in...
- nemetroid 6y ago
  > I just think it's not so useful to compare jet to non-divergent colormaps. I agree, in the "this should be so obvious that it doesn't need an article written about it" sense. But the continued prevalence of jet used as a sequential colour map suggests that the comparison is necessary.
- rozab 6y ago
  I think the reason the example with the photo is useful is because it shows how the colourmap creates features where none exist in the data (due to the nonlinear gradient). When looking at the photo with Jet I can see discrete areas of flat colour, like the Obama 'Hope' poster, but really these boundaries are just artifacts of the colourmap. I think the same thing happens in the arteries example in that SciPy talk. Sure it could be useful in some scenarios to highlight specific parts of the spectrum (like you mentioned with small deviations from the zero point) but at the end of the day the colourmap doesn't know anything about the data and shouldn't make any assumptions. Highlighting certain small intervals in the data could be better achieved with preprocessing, i.e. some polynomial scaling function.
  - blix 6y ago
    If you look at the photo of Curie using any divergent colormap, you get roughly the same effect. The problem is that the colormap is divergent and replaces white with a dark color, not anything intrinsic to jet. If you map this image with BWR or roma you end up with similarly unappealing results. IMO roma is actually the worst of the bunch, despite being the most 'scientific.' Whoever decided that deep, saturated blue and dull brown-red are equally distinct from beige needs to reevalute their model of color perception.