Same colour, different look
Neighbours, shadows and edges change what you see.
How this site works. Every fact is in our own words and linked to its source, beside it. Where good sources disagree, we show each version in a “Sources differ” box. Every picture is our own drawing: we don’t copy the famous originals, we make our own versions of the idea.
The tapestry mystery
In 1824 the chemist Michel-Eugène Chevreul became director of dyeing at the Gobelins tapestry works, and soon got complaints that the colours looked dull. Britannica
He found the problem was not chemical but optical. Britannica
His law of simultaneous contrast: colours placed side by side affect each other, each pushing its own complementary colour onto its neighbour. Britannica
He set it out in 1839 in his most influential book, The Laws of Contrast of Colour. Britannica
He described ways to get colour effects, such as massed dots of single colours. Britannica
He arranged all the colours of the spectrum in a circle to show how they relate. Britannica
Before all that, he patented a new kind of candle, made with stearic acid from fat, in 1825. Britannica
The blue eye that isn’t
In Bach’s eye demo, a grey eye with a red tint around it looks bluish, while the identical grey eye on the other side looks neutral. Michael Bach
The reddish surround pushes the grey towards its opposite colour, which for red is blue-green. Michael Bach
Bach calls it simultaneous colour contrast, probably helped by colour adaptation. Michael Bach
The checker shadow
In Ted Adelson’s checker shadow, a square in the shadow of a cylinder looks brighter than a square outside it. Michael Bach
In fact the two squares have identical luminance: the same amount of light comes from each. Michael Bach
Our eyes are not light meters: they take context into account. Michael Bach
Your brain estimates the lighting and judges the material: is this a light or a dark square, whatever the shadow? Michael Bach
Adelson published it in 1995. Michael Bach
White’s illusion
In White’s illusion, identical bars look different in brightness depending on which stripes they sit on. Michael Bach
Michael White described it in 1979 and 1981. Michael Bach
Lateral inhibition, the usual explanation for contrast effects, predicts the opposite of what you see. Michael Bach
Mach bands
Mach bands: where dark ramps up to light, you see a bright band at the top of the ramp and a darker band at the bottom that are not really there. Michael Bach
They have been known since 1865. Michael Bach
They appear where a gradient of brightness, or colour, bends. Michael Bach
Our view: Chevreul was hired to fix the dye and discovered the problem was the eye. Every painter who ever put a colour next to another owes him a thank-you card.
Next: colour that spreads →