This story makes me remember that I had heard a fun fact a long time ago that many people have never actually seen the colour "violet" which is a single wavelength of visible light. Because there are very few things that reflect only this wavelength in reality. The purple colour we see is formed from a mixture of red and blue, whether it's something in nature, screen displaying or printing. I was so intrigued that I bought a 405nm laser torch and invited some friends to a home party to ‘See the real violet’. That single wavelength of purple really made a different experience, and with good friends, we had a great day.
The olo experiment was very interesting, and it told me that today we even have the technology to stimulate a single cone cell one by one in time. I know that we can't accurately display the olo on screen right now, which also prevents any of these articles from actually containing a picture of the olo. I think it's very close to #00FFEE, and I'm making it the colour of my Hacker News's top bar.
> many people have never actually seen the colour "violet" which is a single wavelength of visible light
The violet seen in a rainbow (in nature, not a photo) is legit single wavelength violet. Same with the rainbows created from shining white light through a prism.
It's true that you don't really get to see it in isolation very often though. Maybe some flowers, birds, or butterflies? Or maybe the purple glow you get from UV lights?
> The purple colour we see is formed from a mixture of red and blue, whether it's something in nature, screen displaying or printing.
Well if it’s on an RGB screen, or printed with CMYK inks then it’s not ‘real’ violet, but there must be plenty of natural and artificial pigments that are actually reflecting violet light and not blue + red light. I imagine any pure compound would be doing this. E.g cobalt phosphate (aka cobalt violet).
You could tell by illuminating a sample with different light sources. See metameric failure:
You did send a specific wavelength to your retina, but that wasn't violet. Because violet is a construct by your brain.
Color is not a property of wavelength. There's nothing special about photons wiggling in the 380 to 750nm range.
In general it's not necessary to be this pendatic, but given the topic here, I think it's important to realize this. It takes a while because we are so good at projecting our internal experience outward.
In my personal conception, violet is the kind of colour at the lower edge of the rainbow, which is a single wavelength. And purple is what the brain constructs. However, of course, the names of the colours are themselves vague.
Hmm if you talk to a colorist violet and purple are 2 different colors one more on the red and the other more on the blue. That’s still the construct of 2 wavelength colors. So a made up color of our brain that doesn’t exist.
The Guardian's article on this[1] includes a quote from an eminent colour expert at City:
> The claim left one expert bemused. “It is not a new colour,” said John Barbur, a vision scientist at City St George’s, University of London. “It’s a more saturated green that can only be produced in a subject with normal red-green chromatic mechanism when the only input comes from M cones.” The work, he said, had “limited value”.
identifying and shining light only on specific type of cells on retina through the iris is of limited value? I personally didn't know we even have that kind of precision.
It's just a typical response. What he means (in an admittedly unnecessary, snarky way) is that this is not going to revolutionise perceptual colour science. It's not going to be an out-of-this-world experience, nor will it change our understanding of how humans perceive colour. I personally think it's pretty cool, though.
This is really fascinating to me. I'm amazed they're able to image the cells of the eye with sufficient resolution and speed to achieve this. From the paper, "and targeting 10^5 visible-wavelength laser microdoses per second to each cone cell.".
If I understand correctly, they first use one type of spectroscopy (AO-OCT) to image the eye and build a map classifying the type of cells, and then use AO-SLO to find the positions of cells in real time. I assume that AO-OCT can't image at a sufficient rate for the second part (or they would just use one type?) so they need to first build this classification map, and then use it to match the position of cells to their type (e g., by overlaying the positions of cells with the classifications and making them line up).
There is a theory that specific shades of colors are difficult to recognize or differentiate unless you name them. I wonder how unique these 100% saturated colors would look without context compared to other colors.
> Five subjects were recruited for this experiment ... Subjects 10001R, 10003L, and 20205R are coauthors on the paper and were blinded to the test conditions but were aware of the purposes of the study. The other two subjects were members of the participating lab at the University of Washington but were naive to the purposes of the study.
Is it normal for the authors to experiment on themselves and their colleagues like this? Or did they not like the idea of laser-stimulating the photoreceptors of random strangers?
I tooke a bodkin gh & put it betwixt my eye & the bone as neare to the Backside of my eye as I could: & pressing my eye with the end of it (soe as to make the curvature a, bcdef in my eye) there appeared severall white darke & coloured circles
Self experimentation is pretty common in psychophysics experiments. I think a big part of it is that the experiments are long and boring, so the scientists themselves are the only people likely to pay attention and perform the task accurately the whole time.
Yes - many psychophysics experiments require a LOT of time and careful attention that would be tricky to get from random participants. It’s often not at all an issue of safety or risk and more just the length, tedium, and motivation.
I swear I remember reading in the 80s about the Air Force having monochrome VR goggles consisting of a per-eye laser, magnetic oil lens for per-pixel depth focus, two perpendicular rotating mirrors for the raster scan and a curved glass lens to reflect and focus the raster scan on to the retina.
Microsoft Research had a project like this at one point, with "goggles" that used lasers on your retina instead of LCDs to project images. No idea what happened to the project, as I haven't heard anything recently.
My shitpost is that they're lucky they didn't trigger a buffer overflow :-) but really, it doesn't seem completely out of question to me that it's possible that some unintended and serious consequence could occur from your brain receiving some stimulus that it doesn't naturally receive. I guess maybe there's no biological analog, but obviously bad things can happen in circuits, computers, etc., when this happens.
The brain is remarkably resilient to that type of issue… Temporary buffer overflow (if you like) can be easily induced and observed with chemicals that modify function at the receptor level; Psychedelics being a classic example. (Worth noting there are many such chemicals used in medicine and research that induce overflow in function besides perception.)
What I find fascinating is the neurological resilience that can be observed at cellular and behavioral levels to bounce back after an event like that.
Non-chemical interventions, like adaption wearing special glasses that flip vision(1), are quickly accounted for by a healthy brain.
An easy way to percieve an oversaturated colour like this is to stare at one colour for a long time, and then switch to its complementary colour. The superposition of the colour and the afterimage of the same colour produces a more intense effect.
The olo experiment was very interesting, and it told me that today we even have the technology to stimulate a single cone cell one by one in time. I know that we can't accurately display the olo on screen right now, which also prevents any of these articles from actually containing a picture of the olo. I think it's very close to #00FFEE, and I'm making it the colour of my Hacker News's top bar.
The violet seen in a rainbow (in nature, not a photo) is legit single wavelength violet. Same with the rainbows created from shining white light through a prism.
It's true that you don't really get to see it in isolation very often though. Maybe some flowers, birds, or butterflies? Or maybe the purple glow you get from UV lights?
Well if it’s on an RGB screen, or printed with CMYK inks then it’s not ‘real’ violet, but there must be plenty of natural and artificial pigments that are actually reflecting violet light and not blue + red light. I imagine any pure compound would be doing this. E.g cobalt phosphate (aka cobalt violet).
You could tell by illuminating a sample with different light sources. See metameric failure:
https://en.wikipedia.org/wiki/Metamerism_(color)#Metameric_f...
You mean few things that reflect only this wavelength? Because I would think anything white would reflect this wavelength just like any other.
The idea I'm having right now is reflecting it off of the rough side of aluminum foil.
Color is not a property of wavelength. There's nothing special about photons wiggling in the 380 to 750nm range.
In general it's not necessary to be this pendatic, but given the topic here, I think it's important to realize this. It takes a while because we are so good at projecting our internal experience outward.
Remember the blue / black dress?
It was, by definition
> Color is not a property of wavelength.
Sure, it's a label
> There's nothing special about photons wiggling in the 380 to 750nm range.
There is - they activate different receptors your brain relies on, hence leading to a distinct (from other wavelengths) sensation
"Purple" is a mixture of red and blue.
> The claim left one expert bemused. “It is not a new colour,” said John Barbur, a vision scientist at City St George’s, University of London. “It’s a more saturated green that can only be produced in a subject with normal red-green chromatic mechanism when the only input comes from M cones.” The work, he said, had “limited value”.
[1] https://www.theguardian.com/science/2025/apr/18/scientists-c...
If I understand correctly, they first use one type of spectroscopy (AO-OCT) to image the eye and build a map classifying the type of cells, and then use AO-SLO to find the positions of cells in real time. I assume that AO-OCT can't image at a sufficient rate for the second part (or they would just use one type?) so they need to first build this classification map, and then use it to match the position of cells to their type (e g., by overlaying the positions of cells with the classifications and making them line up).
Is it normal for the authors to experiment on themselves and their colleagues like this? Or did they not like the idea of laser-stimulating the photoreceptors of random strangers?
I tooke a bodkin gh & put it betwixt my eye & the bone as neare to the Backside of my eye as I could: & pressing my eye with the end of it (soe as to make the curvature a, bcdef in my eye) there appeared severall white darke & coloured circles
https://www.newtonproject.ox.ac.uk/view/texts/normalized/NAT...
What I find fascinating is the neurological resilience that can be observed at cellular and behavioral levels to bounce back after an event like that.
Non-chemical interventions, like adaption wearing special glasses that flip vision(1), are quickly accounted for by a healthy brain.
1:https://www.npr.org/2012/12/14/167255705/a-view-from-the-fli...