UCLA neuroscientist Matt Lieberman posted the 'no red pixels' image on the left. It's developed from an original by Experimental Psychologist Akiyoshi Kitaoka (right). Remember internet kerfuffle that was 'the dress' ? Well, there's another optical illusion that's puzzling the internet right now.
Behold: the red strawberries that aren't really red. Or more specifically, the image of the strawberries contains no 'red pixels. '
This picture has NO red pixels. Great demo of color constancy (ht Akiyoshi Kitaoka) pic. twitter. com/pZHvbB6QHE
— Matt Lieberman (@social_brains) February 27, 2017
The important distinction to make here is that there is red information in the image but, despite what your eyes might be telling you, red is not the highest value for any individual pixel in the image. i. e. there is no pixel that, in isolation, would be considered to be red, hence: no 'red pixel' in the image.
@social_brains I isolated a few of the colors that appear most "red" in the strawberries and put them on the white background to the right. pic. twitter. com/GJJ9PJqNxt
— Carson Mell (@carsonmell) February 28, 2017
As was the case with 'the dress,' it all relates to a concept called color constancy, which relates to the human brain's ability to perceive objects as the same color under different lighting. Which should immediately bring to mind a familiar photographic concept: white balance. Although there's a significant cyan cast to the whole image, your brain is able to correct for it without you having to consciously identify a neutral part of the image (as you'd need to in processing software).
This got us thinking: without any understanding of what strawberries look like, how well would a camera's auto white balance cope with the significant color cast in this image?
Here's what a Nikon D7200's auto white balance algorithms made of the image (defocused slightly, to avoid moir
The answer? Pretty well, actually. We don't know whether it's been able to detect the overall cyan cast or has assumed that the brightest point in the image is probably neutral, but it's done a good job.
We have Experimental Psychologist Akiyoshi Kitaoka to thank for turning this puzzle loose on the world, and neuroscientist Matt Lieberman for turning it viral.
. dpreview.com2017-3-2 23:33