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Speaker 1: Welcome to Brainstoff front House, stuff Works dot Com, where

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Speaker 1: smart happens Him Marshall Brain with today's question, do you

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Speaker 1: remember the polaroid camera with the instant film? How did

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Speaker 1: that film work? How could you take a picture and

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Speaker 1: have the picture developed right in your hand in just

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Speaker 1: a minute or two. Instant camera film is remarkable because

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Speaker 1: it has its own built in developing studio. To understand

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Speaker 1: how this works, you need to understand the basics of

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Speaker 1: traditional photographic film. This has mostly been replaced by digital

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Speaker 1: cameras today, but it's still interesting and it's a great

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Speaker 1: chemistry experiment. Film is a plastic base coated with particles

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Speaker 1: of silver compound that are sensitive to light. Black and

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Speaker 1: white film has one layer of silver compound, while color

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Speaker 1: film has three layers. The top layer is sensitive to

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Speaker 1: blue light, the next layer is sensitive to green, and

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Speaker 1: the bottom layer is sensitive to red. When you expose

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Speaker 1: the film, the sensitive grains of each layer react to

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Speaker 1: light of that color, forming metallic silver at that layer.

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Speaker 1: This gives you a chemical record of the light and

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Speaker 1: color pattern. To turn this into a picture, you have

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Speaker 1: to develop the film. One developer chemical turns the exposed

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Speaker 1: particles into metallic silver. The film is then treated with

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Speaker 1: three different die developers containing die couplers. The three die

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Speaker 1: colors are cyan, a combination of green and blue light, magenta,

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Speaker 1: a combination of red and blue light, and yellow, a

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Speaker 1: combination of green and red light. Each of these die

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Speaker 1: coupler types react with one of the color layers in

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Speaker 1: the film. In ordinary print film, the die couplers attached

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Speaker 1: to particles that have been exposed. In color slide film,

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Speaker 1: the die cup is attached to non exposed areas. Developed

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Speaker 1: color film has a negative image, the colors appear opposite

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Speaker 1: of the colors in the original scene. In slide film,

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Speaker 1: the two dyes that attached to the unexposed area combined

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Speaker 1: to form the color captured at the exposed area. For example,

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Speaker 1: if the green layer is exposed, yellow and cyan dye

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Speaker 1: will attach to either side of the green layer, but

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Speaker 1: the magenta dye will not attach. At the green layer,

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Speaker 1: the yellow and cyan combined to form green. The instant

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Speaker 1: camera developing process combines colors the same basic way that

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Speaker 1: slide film does. It has the same layers of light

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Speaker 1: sensitive grains as traditional film, all arranged on a plastic sheet.

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Speaker 1: The film also contains several additional layers. However, these layers

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Speaker 1: contain all the necessary chemicals for the development process. Underneath

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Speaker 1: each color layer there's a dive aveloper layer containing die couplers.

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Speaker 1: All these layers sit on top of a black base layer,

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Speaker 1: and they sit underneath the image layer, timing layer, and

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Speaker 1: acid layer. This arrangement is essentially a chemical chain reaction

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Speaker 1: waiting to be set into motion. The component that gets

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Speaker 1: the developing process going is the reagent, as in reagent,

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Speaker 1: a mix of a pacifiers, alkali, white pigment, and other elements.

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Speaker 1: The reagent sits in a layer just above the light

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Speaker 1: sensitive layers and just below the image layer. Before you

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Speaker 1: take the picture, the reagent material is all collected in

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Speaker 1: a blob at the border of the plastic sheet, away

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Speaker 1: from the light sensitive material. This keeps the film from

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Speaker 1: developing before it's been exposed. After you snap the picture,

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Speaker 1: the film sheet passes out of the camera through a

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Speaker 1: pair of tight rollers. The rollers spread the reagent material

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Speaker 1: out into the middle of the film sheet, just like

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Speaker 1: a rolling pin spreading out dough. When the reagent is

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Speaker 1: spread in between the image layer and the light sensitive layers,

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Speaker 1: it reacts with the other chemical layers in the film.

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Speaker 1: The obasifier material stops light from filtering into the layers below,

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Speaker 1: so the film isn't fully exposed. Before it's developed, the

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Speaker 1: reagent chemicals moved downward through the layers, changing the exposed

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Speaker 1: particles in each layer into metallic silver. The chemicals then

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Speaker 1: dissolved the developer die, so it begins to diffuse up

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Speaker 1: toward the image layer. The metallic silver areas at each layer.

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Speaker 1: The grains that were exposed to light grab the dies,

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Speaker 1: so they stopped moving up. Only the dyes from the

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Speaker 1: unexposed layers will move up to the image layer. For example,

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Speaker 1: if the green layer was exposed, no bin jet to

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Speaker 1: die will make it to the image layer, but cyane

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Speaker 1: and yellow will. These colors combined to create a translucent

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Speaker 1: green film on the image surface. Light reflecting off the

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Speaker 1: white pigment and the reagent shines through these color layers

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Speaker 1: the same way that light from a bulb shines through

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Speaker 1: a slide. There is one problem left to solve. Recall

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Speaker 1: that there was this opacifier that made it so that

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Speaker 1: light couldn't get in to expose the film. While all

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Speaker 1: this developing is taking place. How do you make the

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Speaker 1: image clear. It turns out that at the same time

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Speaker 1: these re agent chemicals are working down through the light

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Speaker 1: sensitive layers, other re agent chemicals are working up through

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Speaker 1: the upper film layers. The acid layer in the film

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Speaker 1: reacts with the alkali and opacifiers in the reagent, making

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Speaker 1: the opacifiers become clear. This lets you see the image below.

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Speaker 1: The timing layer slows the re agent down on its

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Speaker 1: path to the acid layer to give the film time

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Speaker 1: to develop before it's exposed to light, and you can

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Speaker 1: see it. When you watch the image in a photo

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Speaker 1: film come into view, you're actually seeing this final chemical reaction.

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Speaker 1: The image is already developed underneath. You're just watching the

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Speaker 1: acid layer clear up the opacifiers in the reagent so

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Speaker 1: the image becomes visible to you. For more on this

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Speaker 1: and thousands of other topics, is that how stuff works

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Speaker 1: dot com and don't forget to check out the brain

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Speaker 1: stuff blog on the house stuff works dot com home page.

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