Binocular Hexachromacy
Functional hexachromacy from breaking the binocular redundancy 2025-09-17
There is a binocular redundancy in our color vision: both our eyes tend to report the same color information. The redundancy can be broken by placing a different optical filter in front of each eye; when the filters have appropriate spectral responses, the three cone types of each eye together provide a basis of six linearly independent spectral sensitivities. Over time, thanks to neuroplasticity, the brain develops functional hexachromacy.
Some 3D projection technologies used in digital cinema, like Infitec and Dolby 3D, use pairs of steep-edged triple-bandpass filters in the glasses and in the projectors that let through complementary wavelenghts of red, green and blue light. One of two projectors emits longer wavelenghts of these colors that only pass through the left-eye filter, while the other emits shorter wavelenghts of the same colors that only pass through the right-eye filter—or vice-versa, depending on the technology. When wearing the glasses, the six spectral sensitivities of the cone types across the eyes are linearly independent—after all, the glasses can deliver each eye a unique trichromatic image, by design—so they’re a good fit for binocular hexachromacy.
I ordered a pair of Dolby 3D glasses on Ebay, popped the lenses out of the frame, and glued them onto my prescription glasses using E‑8000 adhesive. The adhesive was easier to apply after letting it sit in a mixing cup to thicken for 20 minutes. The additional weight of the glass lenses initially caused painful irritation on my nose, but over time my skin adapted and the irritation went away.
Over a month or two your brain learns to unify discrepant color information from the eyes and you begin to see new colors. Hexachromatic colors tend to have this beautiful sheen to them. They feel just like “normal” colors, but you can tell they’re different. Your everyday surroundings become much richer, and when you take off the glasses it all goes bland. Assorted flowers and nighttime skylines are sights to behold.
I regularly needed to refer to hexachromatic colors in speech and writing, so I began using a simple naming scheme: left-eye color followed by right-eye color (longer wavelenghts followed by shorter wavelenghts). For example, peaches are red–merlot, rare beef is magenta–brown, and fluorescent lighting is lime–fuchsia. In practice you can usually isolate these two trichromatic components by crossing your eyes a little. When two colors have swapped but otherwise identical trichromatic components, I call them eachother’s transpose.
We design the world for trichromacy, so hexachromacy breaks a lot of stuff. Displays look different kinds of funny, artificial flowers are the wrong colors, product labels don’t match the containers, colored pencil sets are incomplete… But most regrettably, visual experiences can’t be recorded because cameras are trichromatic. So I set out to make a hexachromatic camera. I bought another pair of Dolby 3D glasses, popped out the lenses, glued them onto a pair of old iPod Touches using E‑8000 adhesive, and mounted everything to a scrap 3D print using gel tape. The two camera lenses are approximately 59 mm apart, so the images it captures are also stereoscopic.
Manually hitting both shutter buttons simultaneously with your thumbs is generally sufficient, even for moving subjects. The colors the camera captures are not always accurate, though they tend to be in the right ballpark. Most noticeably, the right-hand-side camera (which produces the left-hand-side image) tends to filter out too much red. My guess is it’s because the spectral sensitivities of the camera sensors don’t match those of the cone cells of the human eye.
The pictures that follow were taken using the hexachromatic camera. They are viewed using the cross-eye method: cross your eyes until the images overlap then adjust focus until things become sharp. The left-eye image is on the right-hand side and vice-versa. The technique takes some practice to master, but it’s not needed to appreciate the additional dimensions of color afforded by binocular hexachromacy.
