Purkinje Effect | Hacker News Reader

Purkinje Effect

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109 pointshypertexthero32 comments

It seems I learn something new every day about our visual system. Thanks for sharing. Last week, it was a link to Technology Connections' video on the colour brown[0].

I also really enjoyed reading Foone's older blog post, "The EYES Have It"[1].

[0] https://youtu.be/wh4aWZRtTwU [1] https://foone.wordpress.com/2019/03/01/the-eyes-have-it/

Brown? You mean Dark Orange right?

Blue leds are so utterly annoying in the dark because even though human color vision is by far the least sensitive to blue light, in the dark the situation is reversed.

Electrical tape has been such a huge friend to me.

Put a powerstrip under my nightstand to service my lamp and the growing universe of chargers? Blue led on it was bright enough to be a nightlight. Tape!

So on and so forth.

Depending on whether you still want the status light, painter's tape or similar can be quite nice.

I use strips from lightdims.com also available from Amazon and other places. Comes in a sheet of precut circles and squares in different sizes so you can stick it over just the LED. Seems to have better sticking power than painters tape. They also have sheets of white / translucent if you want to dim the brightness but still have some color pass through.

Karel Evangelista Purkyně was a fascinating scientist with enormous scope of interest and a very strong ability to think outside the prevailing norms. I wonder what a person like him could do with modern lab equipment.

An anecdote: on his deathbed, he dictated his actual feelings, so that other people would know how the process of dying feels like from the inside. Truly a remarkable and curious mind.

Edit: Jan, Karel was his painting son.

You mean Jan instead of Karel, right?

Yeah, my fault, Karel was his son, a talented painter who died in his thirties. His father outlived him.

I'm unable to find the death notes easily. Could you give me a hint?

I heard it on the Czech public radio more than 20 years ago, in a medaillon dedicated to him. IDK if the notes were ever digitized.

I’m surprised that a Czech name was Anglicized (not sure if that’s the correct word) for this. I’m not used to seeing that. I think I like it? Nothing insignificant grinds me more than watching sports and having Czech names sounded out phonetically via an English approach, and this anglicization is pretty good.

It’s interesting to me because other names like the difficult-to-pronounce Dvořák are kept intact and even attempted quite well by classical fans.

It may dissapoint you to know that in US medicine, body parts like the Purkinje fibers are most commonly called 'Pur-kin-dgee.'

He is also well-known in neurology for his discovery of a particular type of cerebellar neurons, and his name is also misspelled in this field: https://en.wikipedia.org/wiki/Purkinje_cell

There is no way english speakers will pronounce ř correctly, even Slovaks have problem with that.

As a Slovenian to whom Czech sounds like Slovenian with a lisp, how do you pronounce ř?

It’s weird how similar the languages are. Visiting Prague, we could get by on speaking a more proper Slovenian with the locals who spoke back in Czech. Add some hand waving and it worked great.

I don’t quite know how to describe it, so this YouTube video will have to suffice!

https://youtu.be/mM6XJmhFZbI

The way one can learn to say ř is to whisper very very quietly r in a long sequence... rrrrrr. Not [ar] but "just" hard r. Over time, this rolling r can become ř. Children take several months to learn pronouncing it.

They definitely /do not/ pronounce it correctly, but a valiant attempt is made! That’s good enough for me! I’ve noticed most folks pronounce it Dvor-zhak, with a slight but distinct gap added into the pronunciation of the ř.

But like I said, this is leagues better than the butchery I hear when watching hockey, say. :)

I love these HN Wikipedia links and the rabbit hole of open tabs they always send me down. TIL that rod cells in the eye stop sending a signal in response to light.

The Feynman Lectures on Physics also has a very interesting chapter on human vision [1] also describing this effect.

[1]: https://www.feynmanlectures.caltech.edu/I_35.html#Ch35-S1

I never bothered to look it up, and actually thought it was just a name. So, that makes a lot more sense now... one of my favorite power trio bands. Check out "I Rope Steers" for some insane technical chops from the drummer.

https://chunklet.bandcamp.com/album/threads

Wow! Just yesterday I was reading about non-linear effects related to the Cardiac rhythm, where Purkinje fibers play a role: [1]

[1] https://en.wikipedia.org/wiki/Purkinje_fibers

I always find this interesting when it comes to image capture and editing. When designing a camera's imagery circuits for example, do you try to get the picture most resembling actually reality, or the one most resembling human reality; the one where light passes through our lenses, hits a tangle of rods and cones of various densities, and then gets processed in all sorts of weird ways as the jumple of neural signals from those cells make their way into your conscience as an image?

A related advice to those who aren’t professional photoeditors: if you want to substantially reduce brightness, also reduce saturation. Sometimes even reducing only saturation works as intended. This is because in low-light conditions we gradually lose the ability to perceive color. Dim but still colorful objects seem oversaturated.

(I’m not a pro either, but worked at a real typography for a while with guys who knew a thing or two about it.)

Of important interest in practical colour science is the Helmholtz–Kohlrausch effect. More chromatic colours tend to appear brighter, this has direct applications in reducing displays power consumption for example.

https://en.m.wikipedia.org/wiki/Helmholtz–Kohlrausch_effect

Thank you for posting this.

I was reading up on simulating athmospheric and planetary colors based on scattering and sun/moon movement. The formulas told me that the light returned to earth from the moon is red-ish, which confused me. Apparently the reason nights are blue is not because of the light color but our perception of these colors!

“Have you ever seen blood in the moonlight, Will? It appears quite black.”

I have an accessibility red color filter set up on my phone so that I can read in the dark more comfortably, but I didn't know what the effect was called.

I discovered it myself as a kid while looking at red and blue materials of my duvet and duvet cover in the darkness.

This is the effect behind white-and-gold vs blue-and-black dress meme BTW.

I love how blue the evenings look. Green leaves especially.

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