How Does a Polaroid Camera Work?by Edward Mercer
While it may not seem that impressive in the age of digital photography, Polaroid cameras -- and their ability to produce photographs seconds after a picture was snapped -- marked a turning point in the consumer camera industry in the 1970s. Although it has moved into new areas of photography and makes a series of high-tech gadgets, the Polaroid company is still around, and the name is still synonymous with its legendary 1970s cameras and their innovative technology.
Polaroid cameras are loaded with film packs containing sheets of plastic negatives covered in reactive chemicals. When you take a picture, rollers insider the camera remove one negative from the pack and hold it in front of the camera lens. The negative is held in this position for an instant while the shutter opens, exposing the film to incoming light from the lens. After the required exposure time, the camera rollers eject the negative, allowing you to remove the picture.
All analog cameras function in roughly the same way. When you snap a shot, the camera aperture opens briefly to let in the pattern of light reflected from the photographed object. The camera lens's rounded shape takes light going in all directions, and reflects it back into the camera in a single direction toward the film. When the shutter opens, this reflected pattern of light hits the film, which is covered in three layers of silver compounds, each of which absorbs a different primary hue of light -- red, blue or green.
The instant photography of Polaroid cameras is made possible by a chemical reaction under the surface of the silver compounds on the negatives. These chemical layers -- the developer layer, image layer, timing layer and acid layer -- react in the presence of a reagent -- the chemical that sets off the reaction -- to produce the colors captured in the silver layers of the negative. Think of the silver layers as holding the light patterns, while the reacting chemicals permanently turn the color of the light reflected on the negative.
Ejecting the Photo
When the rollers eject the photo, they also press down on the negative to release the reagent chemical held in the white borders of the negative. As the reagent covers the silver surface, it provokes the chemical reaction that produces the image. It takes the picture a short while to fully develop, but the negative slowly turns from gray to a color photograph as the colors set. Contrary to popular wisdom, the Polaroid company actually advises consumers against shaking their pictures during this process.
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