How instant cameras work

Instant or Polaroid cameras are known for developing and printing out photographs within a few minutes after pressing the shutter release button. But how does this seemingly magical process work? The secret simply lies in the film. In order to understand the physics behind instant camera films, it is essential to first become familiar with the basics of traditional photographic film. Traditional film is composed of a plastic base laminated with light-sensitive silver compound. While there is only one layer of silver compound in black-and-white films, color films contain three layers, the first being sensitive to blue light, the second to green and the third to red. Once the film is exposed to light, the individual layers react to the colors, which cause the formation of metallic silver and a chemical reaction. The image created on the film would then have to be further developed, whereas instant cameras already comprise all the necessary chemicals in their films to develop the photographs right away. These chemicals are found within additional layers. A developer layer that contains dye elements is placed underneath each color layer, all of which are underneath the image, the timing and the acid layer and above a black base layer. These several layers are all parts of a chemical chain reaction that becomes induced by a substance called reagent (see images). 

The reagent consists of a mix of opacifiers, alkali, white pigment and other elements and is situated right between the light-sensitive layers and the image layer. As soon as a picture is captured and exposed to light, the film is sent out through a pair of rollers which push the reagent on the white, plastic borders onto the silver compound. This process triggers the four layers to react which in turn causes the silver compound layers to process and produce blue, green and red light patterns. An image is then created and as the photograph starts to appear, a chemical reaction can be viewed.

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