Name of illusion phenomenon of bordering colors

Look at this picture:

enter image description here

All the squares are filled with solid color without any gradient, but at the borders between the colors we see as if gradients were used.

In the past I tried to create similar image by using gradients, but with the time realised that optical illusion gives me the opportunity to create the picture with solid colors without gradients.

I am looking for the name of this phenomenon. Tried to find the name but only “optical illusion” came to results.


The illusion is called “mach bands”

See here:
Mach Bands


The Mach bands effect is due to the spatial high-boost filtering performed by the human visual system on the luminance channel of the image captured by the retina. This filtering is largely performed in the retina itself, by lateral inhibition among its neurons.

The effect is independent of the orientation of the boundary.

Source : Link , Question Author : Ilan , Answer Author : Scott

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