In some of the converted pictures two colors that were different in the original become identical.
If Van Gogh saw colors the way they are in the converted pictures why would he use two different colors that would look identical to him?
If Van Gogh saw colors the way they are in the converted pictures why would he use two different colors that would look identical to him?
So perhaps a better question is, how would you mix the same color twice, if you couldn't tell a range of colors apart?
If he was colour blind surely there would be patches of green and patches of non-green instead of smooth colour. How could he possibly match the same colours over and over again each time he mixed his paints if he couldn't tell the difference?
I'm not an expert in oil painting technique, but I think one possibility is, you tend to overpaint an area at a time. So: mix some paint, layer up part of the canvas. Come back later, mix some paint, do it again.
If that's how it works it would explain a bunch of things in the comparison images. Like: how come the bridge is yellow, but its reflection in the river is bright green? Maybe they were painted at different times.
I think that's what you see in a lot of the pictures. Look at the green in the coat in the self-portrait. What appears as distinct lines of green in the normal color version becomes muted in the modified color version and blends in much more with the other colors, but with just enough difference to lend a rich texture to the coat.
It's also several times more common to be green-deficient than it is to be missing that cone entirely.
I can understand mixing them, or using first one then the other (after you run out of one) - but shading the image partly with one color and parts with another?
The only conclusion is that they were not identical to him, and this software is not correctly showing us what he saw.
While this article doesn't remotely prove that this is what's happened, it seems like a possibility to me.