Speaker 1: Welcome to brain Stuff from House stuffworks dot com where
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Speaker 1: Slash brain Stuff. Him Marshall Brain with today's question, do
Speaker 1: you remember the Polaroid camera with the instant film? How
Speaker 1: did that film? Wark? How could you take a picture
Speaker 1: and have the picture developed right in your hand in
Speaker 1: just a minute or two instant camera film is remarkable
Speaker 1: because it has its own built in developing studio. To
Speaker 1: understand how this works, you need to understand the basics
Speaker 1: of traditional photographic film. This has mostly been replaced by
Speaker 1: digital cameras today, but it's still interesting and it's a
Speaker 1: great chemistry experiment. Film is a plastic base coated with
Speaker 1: particles of silver compound that are sensitive to light. Black
Speaker 1: and white film has one layer of silver compound, while
Speaker 1: color film has three layers. The top layer is sensitive
Speaker 1: to blue light, the next layer is sensitive to green,
Speaker 1: and the bottom layer is sensitive to red. When you
Speaker 1: expose the film, the sensitive grains of each layer react
Speaker 1: to light of that color, forming metallic silver at that layer.
Speaker 1: This gives you a chemical record of the light and
Speaker 1: color pattern. To turn this into a picture, you have
Speaker 1: to develop the film. One developer chemical turns the exposed
Speaker 1: particles into metallic silver. The film is then treated with
Speaker 1: three different die developers containing die couplers. The three die
Speaker 1: colors are cyan, a combination of green and blue light,
Speaker 1: Magenta a combination of red and blue light, and yellow,
Speaker 1: a combination of green and red light. Each of these
Speaker 1: die coupler types react with one of the color layers
Speaker 1: in the film. In ordinary print film, the die couplers
Speaker 1: attached to particles that have been exposed. In color slide film,
Speaker 1: the die couplers attached to non exposed areas. Developed color
Speaker 1: film has a negative image, the colors appear opposite of
Speaker 1: the colors in the original scene. In slide film, the
Speaker 1: two dyes that attached to the unexposed area combined to
Speaker 1: form the color captured at the exposed area. For example,
Speaker 1: if the green layer is exposed, yellow and cyande will
Speaker 1: attach to either side of the green layer, but the
Speaker 1: magenta dye will not attach At the green layer, the
Speaker 1: yellow and cyan combined to form green. The instant camera
Speaker 1: developing process combines colors the same basic way that slide
Speaker 1: film does. It has the same layers of light sensitive
Speaker 1: grains as traditional film, all arranged on a plastic sheet.
Speaker 1: The film also contains several additional layers. However, these layers
Speaker 1: contain all the necessary chemicals for the development process. Underneath
Speaker 1: each color layer, there's a developer layer containing die couplers.
Speaker 1: All these layers sit on top of a black base layer,
Speaker 1: and they sit underneath the image layer, timing layer, and
Speaker 1: acid layer. This arrangement is essentially a chemical chain reaction
Speaker 1: waiting to be set into motion. The component that gets
Speaker 1: the developing process going is the reagent, as in reagent,
Speaker 1: a mix of a pacifier's alkali white pigment and other elements.
Speaker 1: The reagent sits in a layer just above the light
Speaker 1: sensitive layers and just below the image layer. Before you
Speaker 1: take the picture, the reagent material is all collected in
Speaker 1: a blob at the border of the plastic sheet, away
Speaker 1: from the light sensitive material. This keeps the film from
Speaker 1: developing before it's been exposed. After you snap the picture,
Speaker 1: the film sheet passes out of the camera through a
Speaker 1: pair of tight rollers. The rollers spread the reagent material
Speaker 1: out into the middle of the film sheet, just like
Speaker 1: a rolling pin spreading out dough. When the reagent is
Speaker 1: spread in between the image layer and the light sensitive layers,
Speaker 1: it reacts with the other chemical layers in the film.
Speaker 1: The obasifier material stops light from filtering into the layers below,
Speaker 1: so the film isn't fully exposed before it's developed. The
Speaker 1: re agent chemicals moved downward through the layers, changing the
Speaker 1: exposed particles in each layer into metallic silver. The chemicals
Speaker 1: then dissolved the developer die, so it begins to diffuse
Speaker 1: up toward the image layer. The metallic silver areas at
Speaker 1: each layer. The grains that were exposed to light grab
Speaker 1: the dies, so they stopped moving up. Only the dyes
Speaker 1: from the unexposed layers will move up to the image layer.
Speaker 1: For example, if the green layer was exposed, no being
Speaker 1: jet to die will make it to the image layer,
Speaker 1: but cyane and yellow will. These colors combined to create
Speaker 1: a translucent green film on the image surface. Light reflecting
Speaker 1: off the white pigment and the reagent shines through these
Speaker 1: color layers the same way that light from a bulb
Speaker 1: shines through a slide. There is one problem left to solve.
Speaker 1: Recall that there was this opacifier that made it so
Speaker 1: that light couldn't get in to expose the film. While
Speaker 1: all this developing is taking place, how do you make
Speaker 1: the image clear? It turns out that at the same
Speaker 1: time these re agent chemicals are working down through the
Speaker 1: light sensitive layers, other re agent chemicals are working up
Speaker 1: through the upper film layers. The acid layer in the
Speaker 1: film reacts with the alkali and opacifiers in the reagent,
Speaker 1: making the opacifiers become clear. This lets you see the
Speaker 1: image below. The timing layer slows the re agent down
Speaker 1: on its path to the acid layer to give the
Speaker 1: film time to develop before it's exposed the light, and
Speaker 1: you can see it. When you watch the image in
Speaker 1: a photo film come into view, you're actually seeing this
Speaker 1: final chemical reaction. The image is already developed underneath. You're
Speaker 1: just watching the acid layer clear up the opacifiers in
Speaker 1: the reagent so the image becomes visible to you. This
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