1 00:00:00,520 --> 00:00:03,840 Speaker 1: Welcome to brain Stuff from House stuffworks dot com where 2 00:00:03,840 --> 00:00:10,960 Speaker 1: smart happens. This podcast is brought to you by Audible 3 00:00:11,000 --> 00:00:14,280 Speaker 1: dot com, the Internet's leading provider of audio books, with 4 00:00:14,360 --> 00:00:17,520 Speaker 1: more than one hundred thousand downloadable titles across all types 5 00:00:17,560 --> 00:00:20,759 Speaker 1: of literature. For brain Stuff listeners, Audible is offering a 6 00:00:20,800 --> 00:00:22,800 Speaker 1: free audio book to give you a chance to try 7 00:00:22,840 --> 00:00:26,480 Speaker 1: out their service. One audiobook to consider is Blink by 8 00:00:26,520 --> 00:00:30,400 Speaker 1: Malcolm Gladwell. Gladwell delves deep into the human psyche to 9 00:00:30,480 --> 00:00:33,760 Speaker 1: explore how we make decisions. Are people with high i Qes? 10 00:00:33,800 --> 00:00:38,040 Speaker 1: The best decision makers? Not necessarily are hastily made decisions 11 00:00:38,040 --> 00:00:42,080 Speaker 1: the best find out the fascinating science and psychology behind 12 00:00:42,080 --> 00:00:46,000 Speaker 1: the human decision making process in Blink by Malcolm Gladwell, 13 00:00:46,360 --> 00:00:49,839 Speaker 1: available from Audible. To try Audible free today and to 14 00:00:49,880 --> 00:00:52,479 Speaker 1: get a free audiobook of your choice, go to Audible 15 00:00:52,520 --> 00:00:57,800 Speaker 1: podcast dot com slash brain Stuff. That's Audible podcast dot com. 16 00:00:57,800 --> 00:01:05,480 Speaker 1: Slash brain Stuff. Him Marshall Brain with today's question, do 17 00:01:05,520 --> 00:01:10,000 Speaker 1: you remember the Polaroid camera with the instant film? How 18 00:01:10,040 --> 00:01:13,080 Speaker 1: did that film? Wark? How could you take a picture 19 00:01:13,280 --> 00:01:16,240 Speaker 1: and have the picture developed right in your hand in 20 00:01:16,280 --> 00:01:20,440 Speaker 1: just a minute or two instant camera film is remarkable 21 00:01:20,480 --> 00:01:24,480 Speaker 1: because it has its own built in developing studio. To 22 00:01:24,600 --> 00:01:28,119 Speaker 1: understand how this works, you need to understand the basics 23 00:01:28,160 --> 00:01:32,479 Speaker 1: of traditional photographic film. This has mostly been replaced by 24 00:01:32,560 --> 00:01:35,720 Speaker 1: digital cameras today, but it's still interesting and it's a 25 00:01:35,760 --> 00:01:41,000 Speaker 1: great chemistry experiment. Film is a plastic base coated with 26 00:01:41,120 --> 00:01:45,240 Speaker 1: particles of silver compound that are sensitive to light. Black 27 00:01:45,280 --> 00:01:48,440 Speaker 1: and white film has one layer of silver compound, while 28 00:01:48,520 --> 00:01:52,120 Speaker 1: color film has three layers. The top layer is sensitive 29 00:01:52,160 --> 00:01:54,480 Speaker 1: to blue light, the next layer is sensitive to green, 30 00:01:54,880 --> 00:01:57,560 Speaker 1: and the bottom layer is sensitive to red. When you 31 00:01:57,640 --> 00:02:01,960 Speaker 1: expose the film, the sensitive grains of each layer react 32 00:02:02,040 --> 00:02:06,080 Speaker 1: to light of that color, forming metallic silver at that layer. 33 00:02:06,520 --> 00:02:09,160 Speaker 1: This gives you a chemical record of the light and 34 00:02:09,280 --> 00:02:12,720 Speaker 1: color pattern. To turn this into a picture, you have 35 00:02:12,800 --> 00:02:16,960 Speaker 1: to develop the film. One developer chemical turns the exposed 36 00:02:17,000 --> 00:02:20,840 Speaker 1: particles into metallic silver. The film is then treated with 37 00:02:21,000 --> 00:02:25,919 Speaker 1: three different die developers containing die couplers. The three die 38 00:02:26,000 --> 00:02:29,399 Speaker 1: colors are cyan, a combination of green and blue light, 39 00:02:29,639 --> 00:02:33,359 Speaker 1: Magenta a combination of red and blue light, and yellow, 40 00:02:33,400 --> 00:02:36,880 Speaker 1: a combination of green and red light. Each of these 41 00:02:37,000 --> 00:02:40,400 Speaker 1: die coupler types react with one of the color layers 42 00:02:40,480 --> 00:02:44,520 Speaker 1: in the film. In ordinary print film, the die couplers 43 00:02:44,560 --> 00:02:49,040 Speaker 1: attached to particles that have been exposed. In color slide film, 44 00:02:49,320 --> 00:02:54,240 Speaker 1: the die couplers attached to non exposed areas. Developed color 45 00:02:54,360 --> 00:02:57,960 Speaker 1: film has a negative image, the colors appear opposite of 46 00:02:58,000 --> 00:03:01,640 Speaker 1: the colors in the original scene. In slide film, the 47 00:03:01,760 --> 00:03:05,400 Speaker 1: two dyes that attached to the unexposed area combined to 48 00:03:05,440 --> 00:03:09,720 Speaker 1: form the color captured at the exposed area. For example, 49 00:03:09,960 --> 00:03:13,919 Speaker 1: if the green layer is exposed, yellow and cyande will 50 00:03:13,960 --> 00:03:17,040 Speaker 1: attach to either side of the green layer, but the 51 00:03:17,080 --> 00:03:20,400 Speaker 1: magenta dye will not attach At the green layer, the 52 00:03:20,520 --> 00:03:25,080 Speaker 1: yellow and cyan combined to form green. The instant camera 53 00:03:25,280 --> 00:03:30,720 Speaker 1: developing process combines colors the same basic way that slide 54 00:03:30,760 --> 00:03:34,239 Speaker 1: film does. It has the same layers of light sensitive 55 00:03:34,280 --> 00:03:38,080 Speaker 1: grains as traditional film, all arranged on a plastic sheet. 56 00:03:38,520 --> 00:03:43,160 Speaker 1: The film also contains several additional layers. However, these layers 57 00:03:43,200 --> 00:03:48,000 Speaker 1: contain all the necessary chemicals for the development process. Underneath 58 00:03:48,080 --> 00:03:53,040 Speaker 1: each color layer, there's a developer layer containing die couplers. 59 00:03:53,080 --> 00:03:56,480 Speaker 1: All these layers sit on top of a black base layer, 60 00:03:56,680 --> 00:04:00,560 Speaker 1: and they sit underneath the image layer, timing layer, and 61 00:04:00,720 --> 00:04:05,120 Speaker 1: acid layer. This arrangement is essentially a chemical chain reaction 62 00:04:05,360 --> 00:04:09,080 Speaker 1: waiting to be set into motion. The component that gets 63 00:04:09,120 --> 00:04:14,320 Speaker 1: the developing process going is the reagent, as in reagent, 64 00:04:14,840 --> 00:04:20,000 Speaker 1: a mix of a pacifier's alkali white pigment and other elements. 65 00:04:20,400 --> 00:04:24,080 Speaker 1: The reagent sits in a layer just above the light 66 00:04:24,160 --> 00:04:27,839 Speaker 1: sensitive layers and just below the image layer. Before you 67 00:04:27,880 --> 00:04:31,800 Speaker 1: take the picture, the reagent material is all collected in 68 00:04:31,839 --> 00:04:35,320 Speaker 1: a blob at the border of the plastic sheet, away 69 00:04:35,320 --> 00:04:38,920 Speaker 1: from the light sensitive material. This keeps the film from 70 00:04:38,920 --> 00:04:43,200 Speaker 1: developing before it's been exposed. After you snap the picture, 71 00:04:43,640 --> 00:04:46,760 Speaker 1: the film sheet passes out of the camera through a 72 00:04:46,800 --> 00:04:51,320 Speaker 1: pair of tight rollers. The rollers spread the reagent material 73 00:04:51,480 --> 00:04:54,200 Speaker 1: out into the middle of the film sheet, just like 74 00:04:54,240 --> 00:04:58,560 Speaker 1: a rolling pin spreading out dough. When the reagent is 75 00:04:58,720 --> 00:05:02,760 Speaker 1: spread in between the image layer and the light sensitive layers, 76 00:05:02,800 --> 00:05:05,839 Speaker 1: it reacts with the other chemical layers in the film. 77 00:05:06,320 --> 00:05:10,800 Speaker 1: The obasifier material stops light from filtering into the layers below, 78 00:05:11,240 --> 00:05:15,240 Speaker 1: so the film isn't fully exposed before it's developed. The 79 00:05:15,279 --> 00:05:19,360 Speaker 1: re agent chemicals moved downward through the layers, changing the 80 00:05:19,400 --> 00:05:24,320 Speaker 1: exposed particles in each layer into metallic silver. The chemicals 81 00:05:24,400 --> 00:05:28,360 Speaker 1: then dissolved the developer die, so it begins to diffuse 82 00:05:28,600 --> 00:05:32,640 Speaker 1: up toward the image layer. The metallic silver areas at 83 00:05:32,640 --> 00:05:36,799 Speaker 1: each layer. The grains that were exposed to light grab 84 00:05:36,920 --> 00:05:40,240 Speaker 1: the dies, so they stopped moving up. Only the dyes 85 00:05:40,400 --> 00:05:44,000 Speaker 1: from the unexposed layers will move up to the image layer. 86 00:05:44,160 --> 00:05:47,520 Speaker 1: For example, if the green layer was exposed, no being 87 00:05:47,600 --> 00:05:50,200 Speaker 1: jet to die will make it to the image layer, 88 00:05:50,560 --> 00:05:54,440 Speaker 1: but cyane and yellow will. These colors combined to create 89 00:05:54,480 --> 00:05:59,919 Speaker 1: a translucent green film on the image surface. Light reflecting 90 00:06:00,200 --> 00:06:03,720 Speaker 1: off the white pigment and the reagent shines through these 91 00:06:03,760 --> 00:06:07,280 Speaker 1: color layers the same way that light from a bulb 92 00:06:07,400 --> 00:06:11,600 Speaker 1: shines through a slide. There is one problem left to solve. 93 00:06:12,080 --> 00:06:15,640 Speaker 1: Recall that there was this opacifier that made it so 94 00:06:15,680 --> 00:06:18,800 Speaker 1: that light couldn't get in to expose the film. While 95 00:06:18,839 --> 00:06:21,880 Speaker 1: all this developing is taking place, how do you make 96 00:06:21,960 --> 00:06:25,360 Speaker 1: the image clear? It turns out that at the same 97 00:06:25,400 --> 00:06:28,800 Speaker 1: time these re agent chemicals are working down through the 98 00:06:28,920 --> 00:06:33,400 Speaker 1: light sensitive layers, other re agent chemicals are working up 99 00:06:33,920 --> 00:06:37,760 Speaker 1: through the upper film layers. The acid layer in the 100 00:06:37,800 --> 00:06:41,760 Speaker 1: film reacts with the alkali and opacifiers in the reagent, 101 00:06:42,240 --> 00:06:46,200 Speaker 1: making the opacifiers become clear. This lets you see the 102 00:06:46,240 --> 00:06:50,080 Speaker 1: image below. The timing layer slows the re agent down 103 00:06:50,120 --> 00:06:52,680 Speaker 1: on its path to the acid layer to give the 104 00:06:52,720 --> 00:06:56,040 Speaker 1: film time to develop before it's exposed the light, and 105 00:06:56,080 --> 00:06:58,800 Speaker 1: you can see it. When you watch the image in 106 00:06:58,800 --> 00:07:02,920 Speaker 1: a photo film come into view, you're actually seeing this 107 00:07:03,120 --> 00:07:07,680 Speaker 1: final chemical reaction. The image is already developed underneath. You're 108 00:07:07,800 --> 00:07:11,480 Speaker 1: just watching the acid layer clear up the opacifiers in 109 00:07:11,560 --> 00:07:16,680 Speaker 1: the reagent so the image becomes visible to you. This 110 00:07:16,760 --> 00:07:19,360 Speaker 1: podcast is brought to you by audible dot Com, the 111 00:07:19,400 --> 00:07:22,760 Speaker 1: Internet's leading provider of audiobooks, with more than one hundred 112 00:07:22,800 --> 00:07:26,560 Speaker 1: thousand downloadable titles across all types of literature and featuring 113 00:07:26,600 --> 00:07:30,000 Speaker 1: audio versions of many New York Times bestsellers. 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