File talk:Ishihara compare 1.jpg

Why do they have different backgrounds?

They should have the same background to make comparisons easier. Bugefun (talk) 00:24, 7 October 2012 (UTC)

Wrong classification

The samples are completely wrongly labelled (or mixed).

I am deuteranope, and the digit 2 that I see the most clearly is the one shown for the simlation named "deuteranope". The digit that I have the most difficulties to read is the similation labeled as "triteranopia" (though I still read the digit without much difficulty). And I have aboslutely NO difficulties to read all others (including the normal sample).

This image is then completely misguiding and should not be used to illustrate any article. It is completely wrong, becuse its colors were clearly incorrectly computed !

Note that even the English wikipedia article is wrong when it says that deuteranope are dichromat. Most of them in fact really have the capability of seeing 3 basic colors, except that one of them (on the medium-length cones) has a sensibility of the central green wavelength shifted slightly to the red, with a reduced wave length. This means that most deuteranopes can really see a large gammut of colors, except that the perception of differences is reduced between reds and greens, notably on dark shades (i.e. between dark green and brown), or between beige and orange. But deuteranopes actuall have an excellent differenciation of colors of the various shades of yellow-green (which look lighter for them, so they are more easily differentiable, and a huge differentiation between reds and blue, seeing huge differences between shades of rose, violet, fuschia, blue. The also see MUCH more differences of lightness in the greens (more than the 255 levels permitted of green possible in the SRGB standard).

One effect of deuteranopia, is that these people tend to really appreciate the green color in wearings or painting, or in the nature. Their vision of nature offers them more colors than what "normal" people an see (normal people will not differentiate lots of shades of greens that deuteranopes will distinguish more easily). They will perceive also browns often slightly brown, but more importantly they will detect "bluish" effects, notably in natural cyan colors of new leaves. For them cyan is really a very light color, the sky is slightly greenish and never completely blue. The sea will never look blue for them (always cyan, even in images of lagoons).

For this reason, any minor alteration of the level of green in a rendered RGB iamge will make the differences very visible to them, more than waht "normal" people can see. So in summary, the reduced perception of color in some wavelength is in fact largely compensated in other wavelengths, and if more accurate perception of lightness. Deuteranopes are extremely rarely dichromat, most of them are really trichromat.

Forget all what you've read about "color blindness" in Wikipedia, it is commpletely wrong ! verdy_p (talk) 20:47, 4 April 2013 (UTC)