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What is brown

RuvDraba
Posts: 6,033
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6/24/2016 2:42:23 AM
Posted: 5 months ago
At 6/24/2016 1:07:37 AM, janesix wrote:
What is brown? Its not in the color spectrum. So how can we see it?
We don't really see any wavelengths of light, Jane. What we experience as colour is our brain making sense of our eyes' electrochemistry. So some of the colour information we see comes from light entering the eye, some comes from the eletrochemistry of the eye itself, and some comes from how the brain makes sense of the signal. So understanding what we see means understanding what's happening to the signal.

As you know, light entering the eye comes in a spectrum of frequencies, and gets focused at the back of the eye. Rod-shaped cells (simply called rod cells) capture the light and shade of the image, and the brain can use that information to detect edges and textures so it can guess what we're looking at.

But the electrochemistry of colour begins in specialised cone-shaped retinal cells, packed into a tiny pit toward the centre of the retina called the fovea centralis. The fovea features some 4.5 million cone cells, with most of them packed into an area only 1/100th of an inch across. (By comparison there are some 90 million rods, mostly around the edges of the retina.) [http://www.newworldencyclopedia.org...]

There are normally three kinds of cone cells, reacting to light in either a short (blue) medium (green), or long (red) wavelength. Each cell is made from layers of pigmented membrane based on a chemical variant of vitamin A1, a different pigment for each kind of cone.

Cone cells are each connected to a neural synapse buried in the eye. When there's no light of the right frequency coming in, a cone cell constantly sends a chemical inhibitor to keep its synapse quiet. When the right kind of photon comes in, the cone cell stops sending the inhibitor for a while, and the synapse fires. This information travels up the optic nerve, where the brain processes information coming from all the cone cells, and adds (interprets) colour to the image it's already constructing from other information.

So our colour vision is actually interpreted from only three frequencies, and this is why painters can create the experience of the full colour palette from three 'primary colours'. To answer your question directly, our experience of brown comes from stimulating our green and red cones at low saturation, while leaving our blue cones unstimulated. Stimulate them at higher saturation and we'll get shades of orange or yellow instead. [https://en.wikipedia.org...]

But genetic variation gives us slightly different pigments in our eyes, and some rare people (all female) actually get four kinds of cones in their eyes rather than three (and are called tetrachromats.) So we may experience colour differently to one another.

For example, Australian artist Concetta Antico is a tetrachromat, and even though we can't see colours as she does, we can see her fascination with colour in some images I link here: [https://concettaantico.com...]

There are also some sex-based differences in the way male and female brains process colour. [http://news.nationalgeographic.com...]

And there are plenty of optical illusions around colour that help reveal how our brain processes colour information. [https://www.google.com.au...]

I hope that may be useful, Jane. :)
bamiller43
Posts: 200
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6/24/2016 4:01:25 AM
Posted: 5 months ago
At 6/24/2016 1:07:37 AM, janesix wrote:
What is brown? Its not in the color spectrum. So how can we see it?

The same reason we have any color of light that isn't red blue and green (primary colors of light). if an object reflects red and green light, we see it as yellow. Different saturations of red and green make different shades of yellow. Brown is simply another one of those mixtures, same as cyan, magenta and the like.
RoyLatham
Posts: 4,488
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6/24/2016 3:37:43 PM
Posted: 5 months ago
At 6/24/2016 1:07:37 AM, janesix wrote:
What is brown? Its not in the color spectrum. So how can we see it?

Brown is dark yellow or orange. It's a human mental anomaly that while dark red looks red, dark blue looks blue, and dark green looks green, dark yellow looks as if it were a different color, brown. If you put a chocolate bar under a really bright light, it looks orange.