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Wednesday, April 22, 2009

Still about color wheel

This is the follow-up to what I wrote before: hue subdivision for mortals.

Seems everyone echoes my sentiment: increasing the coverage area of green is not the right way to go. The easiest explanation is as follows. Since this is an additive color model, due to the higher sensitivity of green, its contribution to other primary colors should be reduced. Effectively, this means we should shrink the green region in the color wheel:

For the "Mortal" version in the above picture, I modified the conversion from hue to RGB (assuming fully saturated color), because I discarded the idea of curve-fitting to map the angle to the hue value. Another change is that I gave up keeping the triangle of the primaries, i.e. while 0 is still red (as an arbitrary reference), 0.333 is not green anymore. The actual position of a color component is now determined by the inverse proportion of its part to the grayscale function. I arrive at 26% red, 17% green, and 57% blue. Unsuprisingly, it means blue now occupies most of the space.

Under each wheel, shown also colors taken from the color wheel, if it is equally divided into eight parts. The result for "Droid" is probably familiar for a lot of people. Comparing it to the "Mortal" version gives an interesting insight. As can be predicted, now the contribution of green is less dominant. Indeed, blue shades are apparent in few more colors. In fact, this arises a problem. The light and dark blue colors (in "Mortal") look too similar. Compare to the light and dark green (in "Droid"). Maybe this is because the weighting factors of 26:17:57 are completely busted? But then, how shall I come up with nice weighting factors?

Seriously, maybe I should just stop trying all this with an additive color model...

10 comments:

clanehin said...

Maybe this should be done empirically, instead of deductively. Generate a set of a large number of colors covering the spread of colors, and create a web site asking people to rate on a scale whether two colors are similar or different.

This would probably also identify color pairs that are vulnerable to color blindness.

irukado.org said...

Hmm. If you can't provide a triangle of primaries with this model, doesn't it make things a little difficult for those who use colorwheels to choose matching groups of colors?

Also, could this be done at the colorspace conversion level, so that different monitors might display the colorwheel spread according to their capabilities?

Just an idle thought or two :)

Anonymous said...

This one is better, also, red and blue are the true colors for marketing. the effect acquired with even more blue is pretty good.

Anonymous said...

I think the color wheel your previous post looks MUCH better than the "Mortal" wheel. Having all those extra shades of blue wastes space, since the eye can't distinguish between them.

bobthevirus said...

For the next iteration, you could try just reducing the green by some amount, while keeping red and blue proportionately the same. Another option would be to create a whole heap of equally spaced colours using different weightings and get people to choose which ones they think have the most differentiation.

Tim Bocek said...

Personally, I think the colors generated from the "machine" wheel are easier to distinguish. But, as a poster above said, it's probably best to be done as a user study. In fact, you could probably set up a massively collaborative genetic algorithm (where possible weights are optimized and scored by presenting two weights to users at a web site and asking them to pick the better one).

Anonymous said...

i think your idea is fundamentally wrong...

the extra weighting of green in the brightness function only means that a given amount of radiant energy hitting your eye will appear brighter if it happens to be around 555 nm (or about 508 nm if your eyes are dark adjusted). it says nothing about the eye's ability to distinguish between hues at different wavelengths.

color vision is complex. for a quick summary, see

http://www.visualexpert.com/FAQ/Part2/cfaqPart2.html

now, what would be interesting would be to create color schemes for dichromats or anomalous trichromats (ie: colorblind people)....

ray

tech-charles said...

If we can't expand certain colours on the circle without breaking complements and split complements (the reason a wheel is useful in the first place) we need to try an approach that keeps the useful geometry intact.

Suppose we take the 'droid' colour wheel and plot lines from red to cyan, green to magenta and blue to yellow. On the droid wheel the angle between these 3 lines is 60 degrees. Keeping those lines as the colour locations, what happens if we draw a new circle with the centre shifted towards the positive red and positive green axes? It looks promising on the back of an envelope, is this worth further investigation?

tech-charles said...

scratch the above, it's a huge thinko

what happens if the wheel becomes non-circular, stretched outwards in the green region?

prabu said...

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u just visit here
http://u3schools.com/tutorial/html/html_color_wheel.jsp