There as an article that I recently came across (
you can read it here)
that was really fascinating. Dan Dos Santos sent it to me as well and I
thought I would write a quick post about it. It shows a plate of
strawberries (keep reading, that isn't the fascinating part :)).
The contrast has been reduced and the shadow color is shifted to green.
The strawberries look, as you would expect, red. But when you examine
the image closer with the eye dropper tool, you soon see that there is
no red. It seems impossible. The entire image is in fact made of
greens of various saturations.
The article concludes that the reason we see the strawberries as red is
due to "color constancy". The article quotes Bevel Conway, and expert
on visual perception from the National Eye Institute:
Conway said this illusion is also helped out by the fact that we
recognize the objects as strawberries, which we very strongly associate
with the color red, so our brain is already wired to be looking for
those pigments
I think that color constancy is legitimate, and it might add to our
perception in this image, but I don't think it fully explains what is
happening. I believe it is because of a different phenomenon. That is
that
when a gray is placed next to a color of higher saturation and
similar hue and value, that gray will take on the appearance of the
complimentary color.
The reason the strawberries look red is because they are actually less
saturated greens next to higher saturated greens and so they start to
look like the compliment of green. Let's take a closer look at the
image and the palette.
I reduced the image down to 256 colors to simplify the colors and get cleaner color samples. It looks the same at this point:
Here is what the palette (below) looks like for the above image. It is
arranged according to hue. The top rows being a little cooler and
warming as it gets to the bottom rows. Look at how the grays fluctuate
in color temperature according to how much saturation there is.
*if you take the palette in to photoshop, there are a couple pixels in the palette that are outliers
Here is a crop of the image with colors swatches picked out. Note how
in the close up the "red" is still perceived even though you can't
really tell that strawberries are the subject.
The swatches across the top of the image correspond to the pixel at the
center of the circle. Look at how the colors that are more blue or
green are higher in saturation. As the color starts to appear more red,
the hue shifts a tiny amount (still blue/green), but the saturation
drops off significantly and the gray looks more and more red. The most
"red" color, the one 4th from the left is actually the least saturated
color in the crop with a saturation of just 13%.
If we shift the colors more yellow/green, the strawberries start to look purple/magenta:
Here is the 256 color palette for the image above.
This corresponds to the traditional color wheel showing compliments across from each other.
Here is the image shifted more towards blue. The strawberries now look
distinctly orange. If color constancy were the only principle in
effect, we should still see red strawberries, because we know they are
red, but in fact they look orange, reflecting the compliment of blue.
I have written about this in a previous post if you want to see this in action with some paintings:
Feeling Grey Today
I look forward to hearing your thoughts. Thanks!
**update
I created a new image to remove some of the recognizable elements and
just focus on the effect. Here the image has been run through the
mosaic filter, rotated and cropped. I did this to remove any perception
of strawberries. If you take the image into PS and check the value
range of the "strawberries" you will see that there is very little
change in value, just saturation. This is important to get the effect.
Credited to Howard Lyons
Muddy Color post March 7, 2017
http://muddycolors.blogspot.com/2017/03/color-constancy-or-is-it-power-of-gray.html
