Kim Scheinberg

This is a very cool optical effect

Whichever dot you focus on looks purple while the others look blue

As someone whose eyes have been "settling" from cataract surgery followed by a superficial keratectomy in one eye, and has noticed my vision changing daily at various focal points, this is fascinating

https://arxiv.org/pdf/2509.11582v2

Mar 1 at 9:31pmWeb
Show threadToilet full of bugsMar 1
@kims I don't get this illusion at all! I thought it might be because I'm on PC and the image dimensions make me think it's meant to be shown on a phone screen, so I zoomed out. Still all looks purple. I can't make myself see any blue!
Show threadKim ScheinbergMar 1
@ephemeromorph
I read the paper but am not smart enough to understand why it would not work on certain people
Show threadLoïc DenuzièreMar 4
@ephemeromorph @kims I'm on my phone and I don't see anything either, they're all purple no matter how hard I focus on one.
Show threadMees 🔻Mar 10
@tarmil @ephemeromorph @kims I had to turn off all the eye-protecting filters on my phone. But then, it worked. So chances are it's pretty colour-specific
Show threadjon rMar 1

@kims
Usually these images with black and white dots and the likes work for me.

This one doesn't, I don't see the blue dots this time.

Show threadTrezzer (aka Helvedeshunden)Mar 1
@kims All purple all the time for me. But I’m used to my eyes being weird.
Show threadSusan VanderplasMar 4
@trezzer @kims I'm color deficient, and have the same thing. Not sure if my brain is broken or if this is a color vision thing but everything looks purple and nothing flickers like I would expect when I change which one I'm looking at.
Show threadBodhipaksaMar 1
@kims It’s a very striking effect. Very cool.
Show threadDan, the US is the threat!Mar 1
@kims Not sure about the blue, they all look purple to me, however the one I’m focused on is just a tad darker, and it is pretty fast too, almost instantaneous as far as I can tell, which looks like chasing the dark spot around! 
Show threadteresa_athomeMar 4

@WastelandWandrr That's the same effect I see. The dots kind of flicker as my eyes move across them.

@kims

Show threadSpaceLifeFormMar 1

@kims

They all appear blue to me. But I may have cataracts.

Show threadAaronMar 2
@kims So it works if my glasses are on. And it's really weird!

.... if I take my glasses off to get a closer look, it stops.
Show threadWintergreenMar 2

@kims

The one I focus on is purple.

The others are light purple.

Show threadRealGene ☣️Mar 2
@kims
I see the entire row I focus on as purple.
Scale of the display probably has an effect, i.e. phone vs monitor.
Show threadSteve GisselbrechtMar 2

@kims

This is cool because I'm colorblind enough to struggle with distinguishing purple and blue, and all the dots look reliably the same color.

Show threadSusan VanderplasMar 4
@stevegis_ssg @kims ditto. Mildly color deficient, and I don't see anything change the way I expect and others describe.
Show threadClive ThompsonMar 4

@kims

this is wild!

Show threadKim ScheinbergMar 4

@clive
If I were still speechwriting, this would be a slide in a future presentation. There are so many metaphors contained in this

I'll be almost disappointed if it doesn't appear in a @kjhealy talk sometime in the next year or two

Show threadJeanMar 4
@kims only when I squint really hard can I see them all as blue.
Show threadJeanMar 4
@kims but at 2m+ distance they’re all purple
Show threadGreg WhiteheadMar 4
@kims Interesting. I’m red/green colorblind and initially wasn’t seeing the effect, but then I looked at the paper and saw that it’s a distance-dependent illusion, best seen at 30cm (about 12in). At that distance I DO see it faintly
Show threadCarolynMar 4
@grwster @kims I see it at a much closer distance, but, then, am not colourblind.
Show threadPseudo NymMar 4

@kims

Funny you mention cateract surgery. I had one eye done a bit over 3 months ago. The fixed eye makes everything look "cooler" (more blue white) than the unaltered eye (which has a much less severe cateract that "yellows" things a bit)

The illusion works as described on the organic unmodified eye with mild cataract, but no effect at all in the fixed eye.

Wild.

Show threadPseudo NymMar 4

@kims

They are all blue in the fixed eye, and all purple in the unmodified eye, but the focused dot is a darker purple.

Show thread🇨🇦🇩🇪🇨🇳张殿李🇨🇳🇩🇪🇨🇦Mar 4
@kims I got a weird effect. The one I'm looking at looks purple. The rest look blue. EXCEPT the one beneath it. That looks purple too for some reason.
Show threaddxzdbMar 4
@kims @clive I mostly get the light purple effect - only a touch of blue at the edges sometimes.
Show threadRoyMar 4
@kims
Huh. I get darker purple for the dot I focus on and the others are a lighter purple.
The background does look like a shade is blue to me.
Show threadEwen Bell 📸Mar 4
@kims

That is super freaky and breaking my brain.
Show threadJanetDMar 4
@kims I don't see blue dots, but if I quickly scroll the page up or down, I briefly see shadows of the dots.
Show threadChookMother 🇦🇺🦘Mar 4
@kims Not to me.