[0:00] This video is sponsored by Incogn. I
[0:02] made this rubber band that changes color
[0:04] when you stretch it. It's cool, isn't
[0:05] it? It starts off blue, then goes green,
[0:08] and then red, and then when I let go, it
[0:11] returns back to blue. And it's the same
[0:13] mechanism that's used in this
[0:15] 135year-old photography technique that's
[0:18] halfway between a hologram and a
[0:20] photograph. It's the same chemistry as
[0:23] black and white photography. But look,
[0:25] when I change the viewing angle, it
[0:27] bursts into color. And this isn't just
[0:29] any color image. It's arguably the
[0:32] truest color image you'll ever see. And
[0:34] that's because standard color
[0:36] photography is a lie. That's a bit
[0:38] inflammatory, isn't it? Helps with the
[0:40] views. All right. Here's why standard
[0:43] color photography is a scam. So, when
[0:45] you take a picture of something yellow,
[0:47] let's say, then you've got yellow light
[0:50] hitting the sensor of the camera. And
[0:53] that light has a wavelength of about 580
[0:56] nanome. But when you look at the
[0:58] resulting image, you're not getting that
[1:01] wavelength coming from the image.
[1:04] Instead, you're getting some red
[1:05] wavelengths and some green wavelengths
[1:08] that your brain interprets as yellow.
[1:11] And that's because we don't have
[1:12] dedicated cone cells in our eyes for
[1:16] yellow wavelengths of light. Whereas,
[1:18] when I look at this image, all the
[1:20] wavelengths of light that were hitting
[1:22] the plate when the picture was taken are
[1:24] now hitting my eyes as I look at it. And
[1:27] that's because it's basically a hologram
[1:29] except it's encoding color information
[1:32] instead of depth information. For the
[1:34] vast majority of people, you'd never be
[1:35] able to tell, but we can use this
[1:37] spectrum analyzer to see it. So look,
[1:40] this is my phone screen through a
[1:41] spectrum analyzer. And as I move around
[1:44] the image, what you're seeing is just
[1:46] three peaks changing in height. That's
[1:49] red, green, and blue. And they match up
[1:51] with the three types of cones in our
[1:53] eyes. But when I point it at the Litman
[1:55] plate, you can see this complex
[1:57] distribution of wavelengths. And because
[1:59] there are flowers in this image, we're
[2:01] even getting a bit of ultraviolet there
[2:03] as well. Actually, that's a good point.
[2:05] Standard photography doesn't work for
[2:06] other animals, like bees, for example,
[2:09] because they have a different
[2:11] distribution of cones in their eyes. And
[2:14] actually, even for a tiny minority of
[2:16] humans that have four different cone
[2:18] cells and the neurological machinery to
[2:21] use the extra one, the yellow in this
[2:23] Litman plate will look like the yellow
[2:25] they see in real life, whereas yellow in
[2:27] standard photographs would look wrong.
[2:29] So, how is it that this black and white
[2:31] film can reproduce the full spectrum of
[2:34] colors from the real world? Well,
[2:36] they're called Litman plates, and they
[2:38] were made for me by an amazing
[2:39] photographer called John Hilty. I really
[2:42] hope you'll check out his stuff. I'll
[2:44] leave a link to it in the description.
[2:46] And once I had them in my hands, I just
[2:48] thought, well, I have to show this to
[2:49] the world. So, here we are. We're going
[2:51] to figure out together why color seems
[2:54] to magically emerge from this plate.
[2:57] Here's a clue to start with. Watch what
[2:59] happens when I breathe on this plate.
[3:02] See how the whole rainbow seems to shift
[3:05] to the left? Why the heck does it do
[3:07] that? Well, surprisingly enough, it's
[3:09] for the same reason that chameleons
[3:11] change color. Watch this.
[3:16] Yeah, that didn't work. I don't know why
[3:18] I thought that would work. Anyway, we'll
[3:20] get back to chameleons later, I promise.
[3:22] But let's use this rubber band of mine
[3:25] first. We'll call it synthetic chameleon
[3:27] skin because it too changes color for
[3:30] the same reason that a Lipman plate
[3:32] changes color when it's breathed on. So,
[3:34] the way I made this rubber band is I
[3:36] pulled the DVD apart and poured some
[3:39] silicon on this exposed surface inside.
[3:42] In other words, I used that surface as a
[3:44] mold. The surface looks really flat, but
[3:47] it's actually covered in tightly packed
[3:48] grooves. So, now my rubber band also has
[3:51] these tiny grooves in it. And it's these
[3:54] tiny grooves that bring the colors out.
[3:57] So, again, it's not color pigment like
[4:00] the silicon doesn't have any color of
[4:02] its own. It's transparent. Instead, the
[4:04] color comes from the structure of the
[4:06] surface. That's why it's called
[4:08] structural color. And that means if you
[4:10] can change the structure by stretching
[4:13] it, for example, then you can change the
[4:15] color. How cool is that? How a Lithuan
[4:18] play ends up with structural color is
[4:20] amazing. But first, what is structural
[4:22] color? Well, my favorite example is
[4:25] bubbles. Why do you get rainbows in
[4:27] bubbles? Well, let's zoom right in on
[4:30] the bubble film and see what happens
[4:31] when light shines on it. Some light gets
[4:34] reflected and some light gets
[4:35] transmitted from that top surface. Then
[4:38] some gets reflected and some gets
[4:39] transmitted from that bottom surface.
[4:42] And then some gets reflected and some
[4:44] gets transmitted from the top surface.
[4:46] Again, suppose this is red laser light
[4:48] we're shining here. And this is the
[4:50] wavelength. Now, it just so happens that
[4:52] this distance here is exactly one full
[4:55] wavelength of the red light. So you can
[4:58] see that the peaks and the troughs line
[5:00] up perfectly. So when you add them
[5:02] together, you get an even bigger wave.
[5:04] That's called constructive interference.
[5:06] But what if we switch to a blue laser?
[5:08] Well, now this distance is one full
[5:11] wavelength and a half. So now the peaks
[5:14] of this wave line up with the troughs of
[5:17] this wave and vice versa. So when you
[5:19] add them together, they exactly cancel
[5:21] out and you get no light coming out.
[5:24] That's called destructive interference.
[5:26] Now, for in between wavelengths, you
[5:29] wouldn't get perfectly constructive
[5:31] interference or perfectly destructive
[5:33] interference. So, you'd get a brightness
[5:35] in between for intermediate wavelengths.
[5:39] Except what's actually happening here is
[5:41] the light is bouncing up and down inside
[5:44] this soap film multiple times. What does
[5:48] that mean for those in between
[5:49] wavelengths? Well, when you add up loads
[5:52] of offset waves like this, it ends up
[5:55] looking like complete destructive
[5:57] interference anyway. In other words,
[5:59] when you have lots of reflections, the
[6:01] interference becomes really selective
[6:03] and it gets tighter the more reflections
[6:06] there are. So, you end up seeing only
[6:08] that one perfect wavelength of red light
[6:11] that exactly matches and a little bit
[6:13] either side. And the reason you see
[6:15] rainbows is because the angle that the
[6:19] light enters the film at changes this
[6:22] length. So here red light is reflected
[6:25] and here blue light is reflected and you
[6:28] get the full spectrum between these two
[6:30] points. So that also explains why DVDs
[6:33] have rainbows in them except that
[6:35] instead of the light bouncing up and
[6:37] down inside a thin film of soapy water,
[6:40] you've got light that's reflecting off
[6:41] closely packed ridges. So actually the
[6:44] same thing is true for my rubber band.
[6:45] You see different colors at different
[6:47] angles. The difference is that I can
[6:49] shift the rainbow by stretching it. And
[6:51] that makes sense because when it's
[6:53] stretched those ridges become more
[6:55] spread out and so the wavelengths that
[6:57] constructively interfere become longer.
[7:00] And the same thing happens when a
[7:02] chameleon changes color. So a chameleon
[7:04] has these special cells called
[7:05] iridaphors that are packed full of these
[7:09] tiny regularly spaced crystals of
[7:12] guanine. When the crystals are tightly
[7:14] packed, they cause constructive
[7:15] interference for blue light and
[7:17] destructive interference for all the
[7:20] other wavelengths. But a chameleon is
[7:21] able to engorg these cells by changing
[7:24] the osmotic pressure. When the cells
[7:26] expand, the crystals move further apart
[7:30] from each other. This causes the
[7:32] crystals of guanine to spread out so
[7:34] that they constructively interfere
[7:37] longer wavelengths of light. That's not
[7:40] the whole story though. Like chameleons
[7:42] also have a pigment layer. So the final
[7:44] color that you see is a mixture of
[7:47] structural color that the chameleon can
[7:49] tune and this pigment color. Real
[7:52] chameleon skin differs from my synthetic
[7:54] chameleon skin in a couple of ways. The
[7:56] first is that with my synthetic
[7:58] chameleon skin, the interference is
[7:59] happening because of surface ridges.
[8:01] Whereas with real chameleon skin, the
[8:03] diffraction is happening through deeper
[8:05] and deeper layers into the skin. The
[8:07] other difference is that real chameleon
[8:09] skin isn't iridescent, which is actually
[8:11] really impressive. Like, if there's
[8:12] diffraction going on, why don't I see
[8:14] the color change when the viewing angle
[8:17] changes like it does with this mother of
[8:20] pearl or this peacock feather? It's
[8:23] actually a bit easier to see how moro
[8:25] butterflies do it. That incredible blue
[8:28] is also structural color. And just like
[8:31] the chameleon, it looks blue from all
[8:33] angles. To see why, you have to look
[8:36] under an electron microscope. This is a
[8:38] cutaway through the wing. Here's a
[8:40] diagram of it for simplicity. So, the
[8:43] interference comes from these ridges
[8:45] here. So, if light comes directly down,
[8:48] it interferes with this stack of
[8:50] branches, and they're spaced for blue
[8:53] light. Now, if all the branches from the
[8:55] neighboring trees lined up like this,
[8:58] we'd get iridescent. Because look, when
[9:01] light comes in at an angle, it can
[9:03] bounce off this top branch, then the
[9:06] second from top branch on this
[9:08] neighboring tree and so on. And each gap
[9:10] is the same distance. So you've got
[9:13] constructive interference for say red
[9:16] when viewed at this angle. But cleverly,
[9:18] the moro butterfly has all these trees
[9:21] offset randomly at different heights
[9:23] from each other. So when light comes in
[9:25] at an angle, it doesn't see regularly
[9:28] spaced reflectors. it sees a random
[9:30] mess, so constructive interference is
[9:33] impossible. So, you only get reflected
[9:35] light when it's coming straight down,
[9:36] and that's always blue. Chameleons do a
[9:39] similar thing with those guanine
[9:41] crystals, but it's not as easy to
[9:43] visualize. But anyway, we finally come
[9:45] full circle back to the Litman plate.
[9:48] So, when I breathed on the back of this
[9:49] Lipman plate, the gel on the back
[9:51] absorbed some of the moisture from my
[9:53] breath and expanded. And so just like
[9:55] the crystals inside the chameleon skin,
[9:58] the structures inside this plate
[10:00] expanded and separated when engorged
[10:03] with water. And that separation causes
[10:06] the color to shift. But what are these
[10:08] structures inside the Litman plates? And
[10:10] how did they get there? To figure it
[10:12] out, let's look at how one of these
[10:14] pictures is taken. First, take a sheet
[10:16] of glass and coat it in a photographic
[10:19] emulsion. This emulsion is made of
[10:21] gelatin with lots of teeny tiny crystals
[10:24] embedded in it. These are tiny grains of
[10:27] silver haloid, meaning a latis of silver
[10:30] and something like broomemide. You then
[10:32] put the plate face down in a bath of
[10:35] mercury. I don't have any mercury, so
[10:37] you'll have to use your imagination.
[10:38] Now, let's see what happens when the
[10:39] plate is put in a camera and exposed to
[10:42] light. In particular, we'll zoom right
[10:44] in and see what happens when yellow
[10:46] light hits this little section of the
[10:49] plate. First, it passes through the
[10:51] emulsion from the front and then it gets
[10:53] reflected off the mercury bath and then
[10:56] it passes back through the emulsion from
[10:59] the back. And crucially, the reflected
[11:01] light interferes with the incoming light
[11:04] and that creates a standing wave. You
[11:06] know, standing waves, right? The
[11:08] important thing is you've got light
[11:09] energy here at the antinodeses and no
[11:12] light energy here at the nodes. And so
[11:15] these crystals here at the antinodeses
[11:18] start to absorb photons. And eventually
[11:21] as a result, some of the atoms in those
[11:23] crystals break away from the halite
[11:25] atoms and form metallic silver flakes.
[11:28] Just over here, the plate is maybe being
[11:31] exposed to blue light instead. Blue
[11:33] light has a shorter wavelength. So these
[11:35] bands of exposed crystals are closer
[11:38] together. In other words, the color of
[11:40] the light is encoded into the spacing
[11:42] between these bands. After the image is
[11:44] exposed, the plate is developed. And
[11:46] this bit is really clever. So you've got
[11:48] this emulsion with silver haly crystals
[11:51] in it. And some of these crystals have
[11:53] little silver flakes in them from the
[11:55] exposure. And these silver flakes act
[11:58] like a catalyst during development. so
[12:01] that any crystal that contains even a
[12:03] tiny amount of metallic silver becomes
[12:06] entirely metallic silver by the end.
[12:09] There's a final step that flushes away
[12:11] all the silver haly that didn't get
[12:14] converted into metallic silver and what
[12:17] you're left with is lots of tiny silver
[12:20] mirrors embedded in gelatin. Then to
[12:23] view the plate, you just shine white
[12:25] light onto it. And every time the light
[12:27] hits one of the mirrors, some gets
[12:29] reflected and some gets transmitted down
[12:32] to the next mirror and so on. And just
[12:34] like with the soap bubble and the
[12:37] chameleon and the butterfly, the
[12:39] resulting interference produces a
[12:41] specific color that depends on the
[12:43] spacing of the mirrors. In other words,
[12:45] the Litman plate contains a defraction
[12:48] grating that encodes all of the spectral
[12:52] information from the original scene. So
[12:54] why does it only work when it's
[12:56] illuminated from certain angles? Well,
[12:59] with normal pigments, you have light
[13:02] scattering. So white light can hit the
[13:04] pigment from any direction. Some of it
[13:07] gets absorbed, some of it gets
[13:08] scattered, and some of that scattered
[13:10] light reaches your eyes. But when light
[13:13] scatters off a Litman plate, you don't
[13:15] get interference. So you see it as black
[13:17] and white. It's only when the light
[13:19] reflects off the surface that you see
[13:22] the color. Which is why when I shift the
[13:24] focus of my camera lens here, you can
[13:26] see that the light source is reflected
[13:29] there in the plate. You know, Litman
[13:31] plates have their drawbacks. Reprints
[13:34] are basically impossible. Exposure times
[13:38] run to minutes. the restricted viewing
[13:41] angle is less than ideal and they can
[13:45] get a bit washed out if you don't get
[13:47] the process exactly right which is
[13:50] probably why pigment-based RGB
[13:53] photography eventually came to dominate.
[13:56] So, Lipman plates might feel like a
[13:58] historical culde-sac, but it turns out
[14:01] that holograms like this one that can be
[14:04] viewed with reflected white light are a
[14:07] direct descendant of Litman plates. So,
[14:11] you know, thank you, Gabriel Litman. You
[14:14] deserved that Nobel Prize. Right,
[14:16] massive tangent. I love scams. What I
[14:19] mean is, well, I'm interested in
[14:21] everything, including scams. So, when I
[14:24] get a scam phone call, I try and keep
[14:26] them on the phone as long as possible
[14:27] because I'm interested to know like what
[14:29] are their tactics and stuff like that. I
[14:30] don't particularly recommend it cuz you
[14:32] could end up giving away something
[14:34] unintentionally. But let's have a look
[14:36] at an example. This is a phone call from
[14:38] my bank. So, you're
[14:42] >> Yes, you
[14:46] wigs. I thought you'd know my address.
[14:48] >> No, I can send you over a text message
[14:50] now.
[14:52] Yeah. Okay. It's interesting to see how
[14:54] they socially engineer their way around
[14:57] various safety features built into the
[14:59] banking app. For example, there's a big
[15:00] banner in the app that basically says
[15:03] we're not calling you. So like if the
[15:05] bank isn't calling me, who the hell are
[15:07] you?
[15:07] >> Yeah, it's just Okay, I'm just telling
[15:09] you now. It says here, you've never
[15:11] spoke we've never spoken to you on the
[15:12] phone.
[15:13] >> Yeah, that's correct, sir. That's what
[15:14] we've got added onto your account cuz if
[15:16] somebody else has logged in, they can
[15:18] see when's the last time you've been on
[15:19] the call with us here, sir. Maybe you're
[15:21] seeing some red flags here. But the
[15:23] thing that gave it away perhaps more
[15:24] than anything was just how frustrated he
[15:27] was getting with me. Anyway, carry on.
[15:28] So, what what what do you need me to do?
[15:31] >> Are you recording the call, you
[15:34] >> I'm not recording it. Are you genuinely
[15:38] >> Are you sure you're not recording?
[15:41] >> This guy that wasn't very convincing. I
[15:43] just don't think my bank would speak to
[15:45] me like that. It became clear from the
[15:47] call that they had my bank details,
[15:49] which was worrying. And I actually
[15:51] figured out how they must have got it
[15:52] because while he was trying to persuade
[15:54] me of his legitimacy, he read out my
[15:56] email address, but the email address was
[15:58] wrong. It's not the one from the
[16:00] account. It's a random one that I hardly
[16:01] ever use. But I remember I did use it
[16:04] recently for a specific transaction on a
[16:07] camping website. So my guess is that the
[16:09] caller must have used something like SQL
[16:11] injection on that camping website to get
[16:13] my car details. But anyway, every time
[16:15] you put your details into an online
[16:17] form, you're hoping that the company
[16:18] behind it has good security. Obviously,
[16:22] that's not always the case. So, it's a
[16:24] good idea in general to try and minimize
[16:28] how many companies have our data. The
[16:30] good news is that our data has been
[16:32] consolidated to a large extent by these
[16:34] middleman companies. So, if you can get
[16:36] your data off their databases, it can't
[16:38] trickle down to all the others. Not only
[16:40] would you be less vulnerable to data
[16:42] breaches, you'd also get fewer spam
[16:44] calls. The bad news is there are
[16:47] hundreds of these middleman companies
[16:49] called data brokers. And they all have
[16:51] different procedures for requesting data
[16:53] removal. Honestly, if one person could
[16:55] just sit down and do all the hard work
[16:58] of figuring out how to interact with all
[17:01] of these different companies to remove
[17:02] their data, well, I'd happily pay them a
[17:05] little bit of money to do the same thing
[17:06] for my data since they've already done
[17:09] all the research. And of course, that's
[17:11] exactly what I've done. I'm talking
[17:13] about Incogn, the sponsor of this video.
[17:16] It's super easy. You give them your
[17:18] details, you give them permission to act
[17:19] on your behalf, and then they just go
[17:21] away and do it. They also do people
[17:23] search sites, which is reassuring. And
[17:25] on the unlimited plan, you can do custom
[17:27] removal requests if you find your data
[17:30] anywhere out there in the wild. I did it
[17:33] because it turns out that past Steve was
[17:35] doxing future Steve. So, while you might
[17:37] not be able to protect yourself from
[17:39] every camping website that hasn't
[17:41] sanitized its inputs, you can protect
[17:43] yourself from data brokers and people
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[17:50] and use code science at checkout to get
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[17:56] is also in the description, so check out
[17:58] Incogn today. I hope you enjoyed this
[18:00] video. If you did, don't forget to hit
[18:01] subscribe and the algorithm thinks
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[18:07] What's that?