One day I thought long and hard about colour perception and wrote an image filter to try and show people with normal vision how I perceive the world.
It isn't perfect - I can usually distinguish a colour (anything strongly saturated at least) from a non colour (ie grey or very unsaturated colours) but aside from blues and some greens I really can't differentiate them from each other.
Secondly, my blue perception is considerably stronger than normal. Blues appear more vivid and varied to me than to someone with normal vision, so much so that I tend to see colours that have any significant blue hue in them as blue even when they could be some bluish shade of green, for instance.
The filter analyses the hue of every pixel in the source image, based on a self made hue/brightness calibration test (where I matched about 30 points in the spectrum to a greyscale brightness) and reshades the non blue colours to grey, passing only the minimum amount of green I can differentiate (probably not that accurately though). Secondly, it enhances the blue tones, pulling some of the non-blue tones back towards blue in line with the calibration.
All of this was compounded by my CRT's spectral curve so its hardly accurate. However, it might give you some idea:
blue flowersblue flowers - filteredThe second image tends to filter out the sky which in reality looks quite blue to me also, but the filter was probably more than overworked by the flowers ;-)
The point is not so much that everything looks grey to me, as I said, it's more that it is impossible to tell the vast majority of different non-blue colours apart. I haven't found a better way to render this other than simply removing the hue information to give normal sighted people the same perception.
PS:If you get a 403, just enter the url into the address bar directly ;-)
