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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