Human Potential for Hexachromacy 

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Info: Use stereo viewing techniques view the impossible binocular color combinations of this article.

At first glance, the idea that humans could possess hexachromatic vision might raise eyebrows and skepticism alike. After all, suggesting humans can see with six different cone types, compared to the typical three, is indeed a bold assertion. But by the end of this article, not only will you understand the basis for this claim, but you'll have witnessed the seemingly impossible colors for yourself that result from the combination of these six virtual cone types.

The term chromatic redundancy of binocular color vision via binocular fusion of unequal color experiences across two eyes might be familiar to you. In essence, it describes the idea that one eye is already enough for seeing the world trichromatically. The second eye enriches our vision, offering depth and a wider field of view, but it doesn't augment color vision on its own. This leads to an intriguing observation: each eye operates independently. Each eye is a separate visual trichromatic organ. They capture their unique views, and it's only in the brain where these two perspectives merge, crafting the unified image we experience.

This concept of two eyes operating independently holds the key to unlock the potential for hexachromacy of binocular trichromats. With the right blend of ingenuity and novel technology, we can tap disrupt the chromatic redundancy of binocular color vision, opening dimensions of color and visual detail far beyond the ordinary; in both quality and quantity.

In the following we will understand what this entails for human color vision and how this peculiarity of binocular color vision redefines the boundaries of human color perception.

The hypothesis of this article is as follows: 

Binocular trichromatic humans have the potential to become moderately functional hexachromats by intelligently and strategically disrupting the chromatic the redundancy of their binocular trichromatic color vision. This will allow them to distinguish color hexachromatically with a 6-dimensional virtual color space that is populated by new and distinct impossible binocular color combinations that result from impossibly combining different trichromatic colors on the same visual spot across two eyes.

In each of our eyes, there are three distinct cone types responsible for detecting different, but overlapping, wavelength ranges of the electromagnetic spectrum: the S-cone type peaks at bluish light, the M-cone type at greenish light, and the L-cone type at yellowish light. Even though both eyes work in harmony most of the time, presenting us with a unified picture, it's essential to remember that they operate independently. Closing one eye still leaves us with the ability to see colors trichromatically as monocular color vision remains trichromatic.

You might now think: "Red is just red, right?" Under normal conditions, yes. But with the understanding of the six distinct virtual cone types when disrupting the chromatic redundancy of binocular trichromatic vision, we can explore how combining these six virtual cone types' color qualities can produce different color experiences within a single trichromatic color. Let me illustrate this with an experiment, using a saturated and luminous red as an example.

These impossible colors combinations are not a normal retinal blend of two colors. These so-called "non-retinal" (i.e. binocular) color combinations result in very different color qualities for those who achieved adequate functionality in this skill.

Let's experiment with non-retinally combining different shades of the same hue category. Here, we're non-retinally merging the same red hues, but with different saturation and brightness levels.

When we look at these impossible saturation and brightness combinations of a single hue category like red, they render a color palette of their own, presenting a spectrum of distinct impossible reds in the above example. Despite the differences, they all resonate with the identity of the one eye's singular pure red, and thus can be identified as its variations in context.

The phenomenon we're observing with these impossible red colors isn't unique to this specific hue category; every trichromatic color holds this potential. Considering the vast amount of combinations possible on a typical RGB screen, we can create about 8 million distinct impossible color combinations for each normal trichromatic color we see. And that's already when excluding color doubles (like red/green and green/red).

To illustrate the sheer magnitude of the number I've just hinted at, here's a perspective: On a standard screen, normal trichromats can discern about 16 million individual trichromatic colors. Multiply this amount by the 8 million impossible variations, and we arrive at a staggering number of about 140 trillion distinct impossible colors. Trying to visualize this number is mind-boggling.

Let's simplify the complex techniques I've presented here into two digestible concepts. 

Dynamic examples of such impossible colors are preferable because they let each person select non-retinal (i.e. "impossible") color combinations that their visual system and brain can more easily fuse binocularly. The below Stereo Trichromatic Color Mixer application allows for such dynamic and modifiable non-retinal color combinations. It also shows the retinal color combination of the selected colors of the left and right dots below.

These isolated examples of non-retinal colors are already helpful, but seeing them in a hexachromatic color space better demonstrates what it means to see a volume of colors for every single trichromatic colors. The below 6-Dimensional Hypercube [...] application demonstrates an approximation of the hexachromatic color space that's possible with disrupting the chromatic redundancy of binocular trichromatic color vision. The program doesn’t attempt to show every non-retinal trichromatic combination: displaying 256^6—over 280 trillion—dynamically animated colors in a stereo-simulated six-dimensional color space would overload most systems. In the following program, even a relatively small cube resolution of more than 3x3x3 will probably cause frame drops.

Once your eyes are aligned, even if it feels a little wobbly, instable or the color seems to shift, you'll be able to observe their difference. All colors should pop out as distinct from each other. For some people, especially for beginners, an impossible color like this might look a bit like the color that you get from retinally mixing the two compounds, as seen surrounding the white dots. But you can definitely spot the difference and appreciate each color for its uniqueness, even if the colors are as similar to each other as in the example of verd (i.e. a non-retinal vermillion-red).

One remarkable aspect of this technique is how it reveals that seemingly the same impossible color can create visible differences when viewed laterally interchanged. Even if both colors essentially evoke the same non-retinal color quality without sufficient context, your eyes can pick up the distinctions in an adequate and adjacent context.

This is the charm of impossible colors. They challenge our perception, expanding the boundaries of what our eyes can see and and what our brain can understand. These few examples are just a sample of the vast world of impossible colors.

There are about 140 trillion unique impossible trichromatic color combinations. This is a number that's difficult to conceive. Presenting them all at once on one screen is currently impossible. Yet, even tapping into a tiny slice of this vast hexachromatic color space can revolutionize the way we perceive color.

My applications Color in Color and Custom Color Vision are designed to realize this potential for human hexachromacy of binocular trichromats—even if it's in the context of a 3D trichromatic color space. The Custom Color Vision will soon be released and purchasable on itch.io, Ooqui Sensory Lab. Developing Color in Color will still take some time. Both Color in Color and Custom Color Vision fundamentally redefine human color vision.

As creatures who navigate the world mainly through vision, we are inseparable from color (even in the case of monochromats). Multiplying the volume of colors we already know by a factor of eight million is an experience so far beyond ordinary sight that words can barely convey it. Mastering the stable perception of “impossible” binocular/non-retinal color combinations has the potential to transform everything from art, film, and video games to medical imaging, chemistry, and astronomy, and so much more. By disrupting the chromatic redundancy of binocular chromatic vision and weaving these non-retinal color combinations into even a standard digital 3-dimensional color space, we can unlock patterns and details that were once indistuinguishable—an indescribable expansion of the visual world for anyone who learns this skill and has the right to technology to functially generate this impossible color vision.

The dimensions of color vision are far vaster and more intricate than we often give them credit for. The immensely enhanced color vision that you have experienced today—though still just a tiny fraction of what is actually possible—results in a world of hexachromatic color; technically, practically and literally speaking. While naturally different to "real" hexachromacy, this non-retinally mediate hexachromacy by disrupting the chromatic redundancy of binocular chromatic vision is moderately functional and can yield hexachromatic color qualities.

The Color in Color method has demonstrated layers of color perception previously thought impossible, challenging our basic understanding of color. By implementing this complex non-retinal interplay between hue, saturation and brightness into our vision, and making use of the combined might of both eyes by disrupting chromatic redundancy, we're not just adding colors to a palette—we're revolutionizing the canvas itself by extending into three additional color dimensions.

My applications Color in Color and Custom Color Vision serve as functional tools that enable us to look into and see with this expanded dimensionality of color—with the power to transform everything visible. From art and media to the simplest everyday sights, the potential is incredible. As we stand before this visual revolution, it becomes clear that normal trichromatic vision, ever so intricate in even its natural form, still is but a tiny fraction of what can actually be seen.