Optical illusion goes viral: Can you see black and white or colour?

Danielle Fowler
Freelance Writer

A clever optical illusion is doing the rounds and it’s leaving people baffled.

The series of images, shared by Lionel Page, an economist at UTC Economics, and created by software developer and digital media artist, Øyvind Kolås, have been doing the rounds on Twitter due to their ‘colour assimilation grid’ illusion.

The photographs appear to be in colour but they’re actually black and white.

Kolås explains on his website that the images are part of a visual experiment that uses “very-saturated coloured grids overlayed on a grayscale image.”

These cause the grayscale cells to be perceived as having colour, he adds.

The incredible technique is similar to the way that printers use colours: the colour mix is seen by the eye and interpreted by our brains to create the final image.

The image has garnered attention as we all see colour differently.

According to Pantone, the human eye and brain work hand-in-hand to translate light into colour.

Objects have colours because they reflect these particular wavelengths of light while absorbing other wavelengths.

For instance, the colour red is not ‘in’ an apple. The surface of the fruit reflects the wavelengths we perceive as red and absorbs the rest.

These wavelengths then travel to the eye using photoreceptor cells known as rods and cones.

There are 120 million rods which detect mainly black and white information while approximately seven million cones detect different wavelengths of light roughly corresponding to green, red and blue.

We see colour because the brain pieces together all of the information collected by the rods and cones - often filling in “missing” parts in order to understand our surroundings.

Words by Danielle Fowler

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