Comment by dietrichepp | Hacker News Reader

Comment by dietrichepp | Hacker News Reader

Parent Full thread

Quick summary of how it works: it's a passive filter, no electronic components. Nothing magical, but it is designed in a very clever way.

Our eyes have three types of cones, call them L, M, and S (you might think "RGB" but it's really not, but that's not a bad lie to believe). Between L and M, for example, there is a fair bit of overlap. So, these glasses filter out the colors in the middle, where L and M overlap the most. This means that the only colors which make it through are the colors which your eye can distinguish better, making the colors more vibrant.

This works because most colors are a mix of a bunch of different frequencies of light. Say, ROYGBIV. Maybe you have color blindness and a ROY mix looks the same as an OYG mix. These glasses will filter out OY, so you are left with R in one mix, and G in the other mix. These are easier to tell apart.

So, obviously not perfect, but it doesn't need to be. It just needs to be better than what nature gave you (if you're colorblind). It also doesn't work for people with, say, 100% deuteranopia, but most people with color blindness aren't that severe.

So it's an optical notch filter?

It doesn't shift anything, just blocks the ambiguous "inbetween" colors.

Yes.

This means they're more like a hearing aid (shifting frequencies you're unable to hear into the spectrum your ear can process and simply adjusting loudness) than a "cure".

I'd want to try one out for the kick of it, but I can't imagine using it the way I would use regular vision-correcting glasses (or contact lenses). Possibly as an aid for driving (where colour vision can be critical) but not as a part of my everyday life -- much like Gunnar glasses, which I only use at work.

I guess I'll have to wait for gene therapy or bionic technologies to advance to the point where I can actually get something that lets me see colours properly.

Or, heck, tweak these so they shift IR or UV into the visual spectrum and they'd have my attention.

EDIT: Emulating "normal" colour vision is interesting but emulating mantis shrimp colour vision would make the glasses worth the price tag.

They're hearing aids in reverse. They filter out light instead of adding to it. Still, I'm colorblind, and when I tried them on in sunlight, it was an amazing experience. Maybe not a cure but damnit if I'm not happy these things now exist! Seeing that a carrot was orange instead of green for the first time was mind blowing and emotional. Enchroma will open a whole new market that might lead to a cure! Until these glasses started going viral, color blindness was an invisible disability that the real world mostly ignored despite its prevalence, because there was no market in fighting it.

Explanatory note: Most humans have three types of color receptive cones; a few have four. Mantis shrimp have sixteen.

Fewer cones may be better for low-light vision. Apparently mammals grew out of a evolutionary niche where this was important, and they generally only have two cones while other vertebrates have four. Remember how dogs have poor color vision? That's true of almost all mammals. Primates are unusual among mammals in having 3 types of cones and better color vision. Meanwhile reptiles, birds, amphibians, insects have 4 types of cones and much better color vision than us.

The eye has a limited amount of real estate for light sensitive cells, and animals have a limited amount of energy to dedicate towards eye growth. More cones generally means fewer rods, which means poorer night vision. You can see this for yourself at night, because cones are concentrated at the center of the field of vision and rods are more common at the periphery. A common trick in astronomy is to look next to a star rather than directly at a star, it is not too hard to find stars which are invisible when you look at them directly but which become visible when you look to the side. Various nocturnal and deep sea creatures also feature a number of different adaptations, such as the tapetum lucidum (which reflects light to pass through the retina a second time) and special inverted rods which increase light sensitivity. These structures come with their own various tradeoffs. For example, the tapetum lucidum reduces image sharpness.

In spite of this, humans have very good eyes, with a balance of good low-light vision, good color vision, and good image sharpness. There are other animals better at each of these, but humans are still pretty amazing.

Just to clarify why calling it RGB isn't that wrong, for people who don't understand the LMS thing[1].

LMS stands for Long/Medium/Short (wavelength) cones, and I assume most of us know RGB is Red/Green/Blue.

Long cones are responsible for seeing long wavelengths ("λ") of the visible electromagnetic spectre ("EMS") are going towards Red and peak there before fading into infra-red.

Medium cones are responsible for seeing the medium λEMS peak at green, where the Short cones kick in for short λEMS, and they peak at blue.

Some colours are seen when two (or maybe even all three?) cones are simulated: Orange, Yellow, Cyan, Purple, etc.

--- [1]: I'm not an expert on the subject, bit I did some research into it because a friend of mine is partially colour blind.

The reason why I call RGB "wrong" is because the L and M cones both have peak sensitivities to greenish light. So the three cones would be something like "yellowish green" (564-580 nm), "bluish green" (534-545 nm), and "violet" (420-440 nm). It is a common misconception that long cones are mostly sensitive to red. People often say that, but it would be more accurate to say that long and medium cones are both mostly sensitive to green light.

At least two cones are usually stimulated, and often all three, even by monochromatic light. Color is perceived by the differences in stimulation between cone types.

RGB is a model which allows us to reproduce color, and it is useful because it can be mapped to LMS using a linear transformation. However, RGB is not how we perceive light.

Reply on news.ycombinator.com