[HN Gopher] Ask HN: Why does this image look 3D?
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Ask HN: Why does this image look 3D?
The image: https://twitter.com/mrbiffo/status/1516862012915167236
Mirror: https://i.imgur.com/3TU00N4.jpg On my Mac's Dell LCD
monitor, this image has a surprisingly intense 3D effect. The
colored blocks appear to be floating in front of the blue and black
background. On my iPhone, the effect doesn't work at all, and it
appears completely flat. This is not simply a parallax or
contextual effect - it feels as if I am looking at one of those
lenticular 3D postcards. What's going on?
Author : LeoPanthera
Score : 33 points
Date : 2022-04-20 19:58 UTC (3 hours ago)
| TheRealNGenius wrote:
| it doesn't?
| sys_64738 wrote:
| Because it's using black to convey perspective of an alleyway.
| 3qz wrote:
| My old Samsung S9 made this colour of blue on black look 3D and I
| have no idea why. Links on a black page popped out. On iPhone it
| doesn't. Do you have another device to test on?
| rantallion wrote:
| I'm not sure about the floating blocks but I feel I should let
| you know: the background is white and gold.
| dhritzkiv wrote:
| Not getting the effect, personally.
|
| Viewing on a 2017 5K iMac here; don't wear glasses (as others
| have mentioned eyewear impacting their perception)
| bXVsbGVy wrote:
| I think is only noticeable on mobile phones.
| qwertox wrote:
| Me neither, with glasses. There is the "3D" effect from the
| perspective of a known silhouette when looking down a street at
| night, but this is more due to the association of the central
| perspective with 3D depth instead of some weird effect.
|
| It looks completely uninteresting to me.
| apolloartemis wrote:
| I'm just speculating so someone else might know better. What I
| think is going on is that if your monitor shows especially short-
| wavelength blues, since this image uses pure #0000FF blue, it's
| possible that the blue is so pure and short-wavelength that the
| lens of your eye doesn't focus those pixels quite right, and it
| ends up at a different focal plane than the other colors,
| especially the pure red which is very long-wavelength.
|
| The iPhone might use less extreme wavelengths for the colors, or
| use LEDs that are less spectrally-pure.
|
| Edit: like the user named Someone commented below, it looks like
| this phenomenon has a name - chromostereopsis.
| barrystaes wrote:
| I dont think the blue wavelength is it, but a cool fact: humans
| can only see blue in true focus when under water! This is why
| you dont want blue text for signage. Backgrounds on traffic
| signs are ok if the text on it has high contrast and its a
| reflective material.
|
| Refraction for blue from lens to air is not aligned like red
| and green are.
| lifthrasiir wrote:
| I wear glasses and still don't get the effect from my main
| display. I only realized it can be seen as 3D after seeing two
| street lights in different sizes. To me it looks more like two
| tall buildings with multiple bridges.
| postsantum wrote:
| For me it's 3D if I wear glasses and flat if I remove them.
| Curious!
| Sohcahtoa82 wrote:
| Do your glasses produce any level of chromatic abberation? If
| so, that would explain it.
|
| For my glasses, blue tends to get pushed slightly to the
| outside of the center of my vision and red gets pushed towards
| the center. At the center of my vision, I don't notice it, but
| if I look towards the edge of my lenses, it's pretty apparent.
|
| This abberation will cause a significant shift when looking at
| pure reds and blues, creating the 3D effect.
| postsantum wrote:
| Yeah, I looked at it closely and there is a thin black line
| on the edge between red and blue that is getting wider as I
| look at it through thicker parts of the lenses. Basically, I
| move my head and see "another side" of the box that doesn't
| exist
|
| OP, I think we figured this out
| nullc wrote:
| I bet you wear glasses with polycarbonate lenses.
|
| I dunno how people stand optics with such high CA. CR-39 is much
| better optically and also a lot less expensive-- vendors shovel
| people into polycarbonate because they can charge more for it.
|
| E.g. from zenni CR-39 lenses are 'free'! but you have to click a
| bunch of extra times to choose them.
| wincy wrote:
| Not op, but.
|
| Interesting you mention that because I'm wearing Zenni glasses
| and went and checked on my orders page that they're not
| polycarbonate. I got the "free" lenses with oleophobic coating.
| This image doesn't look 3D at all to me. I was very confused
| about this post.
| dandongus wrote:
| Not seeing it brah
| Teletio wrote:
| It's an optical illusion. Your brain knows how 3d a alley should
| look like.
| throwaway743 wrote:
| Blue recedes, red brings objects forward. It's taken to the
| extreme with the high chroma of the chosen colors, giving a 3d
| effect.
| MarcScott wrote:
| My brother and I once had an idea for a 4D game, where you
| could be chased by NPCs that could move in 4 spatial
| dimensions. As well as perspectively increasing in size as they
| came closer to you in 3 dimensions, they would red and blue
| shift to indicate the 4th dimension.
| lurquer wrote:
| Seeing it on an old iPhone.
|
| Very vivid.
|
| The reason is the blue/red wavelength thing discussed herein.
| Pretty standard optical illusion. But the RGB values and shapes
| are configured to create a better demonstration of this than I
| have ever seen!
| o_m wrote:
| Are you high?
| Someone wrote:
| Possibly https://en.wikipedia.org/wiki/Chromostereopsis
| theandrewbailey wrote:
| Does this happen with other images? Do you wear glasses?
|
| I do, and moving that image around my field of view gives a mild
| 3D effect. I've always suspected that my poly carbonate lenses
| have strong chromatic aberration[0], with reds being separated
| outwards (blues inwards) when viewed towards the edge of my
| lenses.[1] When moving that image around, the red areas move more
| than the blues, so yeah, that's a fake 3D effect.
|
| [0] https://en.wikipedia.org/wiki/Chromatic_aberration
|
| [1] this is especially noticeable when I look at Microsoft's logo
| with the colored squares. I know that they are supposed to be
| equally spaced out, but they almost never look that way to me,
| especially when viewed in thumbnail form.
| Sohcahtoa82 wrote:
| I think this is it.
|
| My glasses have a noticeable aberration when I look at the
| edges of the lenses. This image gives me a slight parallax when
| I look around with my glasses on, but if I take them off, it
| doesn't happen at all.
| LeoPanthera wrote:
| I do wear glasses! And I think you're onto something. I just
| switched to my backup pair and the effect is much less
| pronounced. So it must be something to do with my glasses.
| bananabiscuit wrote:
| You are probably seeing the effects of chromatic aberration.
| Bluer colors get refracted more strongly than redder color.
| The thing that makes it look 3d is that this effect is more
| pronounced the further from the center of the lens you are
| looking. So in your left eye for example the yellow boxes are
| closer to the center of the lens than in your right eye, the
| chromatic aberration will shift those yellow boxes more in
| your right eye relative to how the blue background gets
| shifted, and that results in what your brain perceived as
| parallax which makes you think the image is 3D.
| rahimnathwani wrote:
| > I do, and moving that image around my field of view gives a
| mild 3D effect.
|
| Same for me. I tried with two different pairs of glasses (both
| from Zenni).
|
| Without glasses there's no such effect.
| ungawatkt wrote:
| I think you're on to something, while I can still "force" a 3D
| effect on the image without my glasses by unfocusing a bit and
| moving the screen, it's much stronger with glasses on.
|
| Edit: nearsighted, I don't remember the glasses prescription
| but contacts are -3.25
| aimor wrote:
| This has annoyed me for years with my polycarbonate (or some
| other plastic) lenses. I do a lot of work plotting data, and
| people like to use vibrant colors with pure red, green, blue.
| Well I turn my head slightly and the lines shift, or they split
| into two different colored lines.
|
| With a prescription around -6 I'm not sure what the best
| alternative is, I was looking into glass lenses again.
| foobarian wrote:
| Recently I inquired about glass lenses for that reason after
| a long time with plastic ones, and was surprised to learn
| they are mostly phased out due to safety concerns.
| alar44 wrote:
| You for sure don't want glass lenses. Your biggest issue
| isn't poly, it's your lens thickness. Best way to get the
| thinnest lenses possible is to use round frames. Perfect
| circles would be ideal, rectanglish in any way is going to
| thicken them significantly. Mention those issues to your eye
| doctor too, they'll know how to reduce abberation with
| different lens designs if that's something that bothers you.
| louissan wrote:
| Because its ascii art inspired from cyberpunk 2077 xD
| manifoldgeo wrote:
| There are a lot of answers here that suggest the colors have
| something to do with it. I think that is true, but no one has
| suggested what I think it is overall: the Gestalt Principles[0]
| in action.
|
| The Gestalt Principles are from cognitive psychology, the part of
| psychology that deals, in part, with how we sense (eyes) and
| perceive (brain / mind) visual stimuli. Those principles are used
| a lot in interaction design, UX design, human-computer
| interaction, etc.
|
| The specific Gestalt principle at work here is likely the "Figure
| / Ground" principle, also known as "background-foreground". Our
| brains are somewhat pre-wired to see things as either being in
| front or back of other things. There are some optical illusions
| that mess with our perception of foreground, e.g. Rubin's
| Vase[1].
|
| The picture in question has the buildings in black, indicating
| they're silhouettes because the light source isn't hitting the
| walls directly. The blue of the background suggests some light
| coming from the night sky, illuminating things from the back. The
| brightly colored signs would provide their own light in the real-
| world context, and they have a high luminance value[2], i.e. high
| perceived value of lightness, as if giving off their own light.
|
| To sum it up, it looks 3d because our brains have evolved in a
| three-dimensional world and have built-in functionality that
| helps us "fill in the blanks" in situations with incomplete
| information.
|
| References:
|
| [0]: https://www.interaction-
| design.org/literature/topics/gestalt...
|
| [1]: https://en.wikipedia.org/wiki/Rubin_vase
|
| [2]: https://vanseodesign.com/web-design/color-luminance/
| LeoPanthera wrote:
| This might help, but I'm confident this is not the primary
| cause, here. The effect I can see is not that of the buildings
| receding, but of the colored blocks floating off the surface of
| my monitor. They even seem to exhibit a small amount of
| parallax if I move my head.
| noone_youknow wrote:
| iPhone 13 pro max here, see it as 3D. Pretty trippy!
|
| (Also yes, glasses)
| chadcmulligan wrote:
| Red and blue are the extremes of colours we can see, and because
| of the change in wave length they focus at different lengths in
| our eye. So to focus on either colour your eye has to adjust its
| focal length, which gives the 3d effect. The perspective probably
| adds to it.
|
| It's called chromostereopsis -
| http://en.wikipedia.org/wiki/Chromostereopsis
| ricardobeat wrote:
| Why doesn't it work as well on a mobile phone though?
| Especially since an iPhone has better color reproduction than
| most desktop monitors.
| herpderperator wrote:
| I think it may also depend on the subpixel geometry[0][1]
| (and pixel density) of the screen. There are a lot of ways to
| arrange subpixels.
|
| [0] https://en.wikipedia.org/wiki/Pixel_geometry
|
| [1] https://en.wikipedia.org/wiki/PenTile_matrix_family
| tomilola39 wrote:
| Here's the iPhone 13:
| https://www.displaymate.com/Diamond_69M.html
| pwillia7 wrote:
| This hurt my eyes more than any image I've ever looked at
| -- desktop monitor. Ow.
| dudus wrote:
| Came here to say this, and also that I like this other page
| with a good explanation of the phenomenon.
|
| http://www.ritsumei.ac.jp/~akitaoka/scolor-e.html
| bXVsbGVy wrote:
| Probably because one of those two facts:
|
| 1. The blue light is physically behind the others wavelength;
|
| 2. The blue is (much) more intense than other wavelengths.
|
| Some background.
|
| The LCD panel is a RGB filter in front of a white light.
|
| White light is usually* made with a blue diode with some phosphor
| on top. The phosphor converts some (but not much) of the blue
| light into the rest of visible spectrum. Most of emitted light is
| the original blue from the diode.
|
| Fun fact: The sun is also mostly blue. And there are white lights
| that are pretty much only blue, but we perceive as white (usually
| sold for vegetative growth of plants).
|
| * In the past we used fluorescent tube. Quantum dot film are
| becoming common now (they have been used for a while, but are
| mainstream now because Rec. 2020). There are white diodes, but I
| haven't heard about them being used as backlight -- their CRI are
| pretty terrible, and they are expensive.
| kilovh wrote:
| the effect can be much stronger, try this one
|
| https://imgur.com/0htzt9Y
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(page generated 2022-04-20 23:01 UTC)