How does a Polaroid camera work? A Polaroid camera technically works in the same way as a regular camera, except that all of the chemicals needed to develop the photograph are already inside the photographic film that is inside the camera.
These days, we mostly use digital cameras or our phones. However, back in the day, cameras took images that were recorded on film, and that film needed to be processed, which you could do yourself or which you could get done in a shop, usually a drugstore. The film in the camera is made of clear plastic, and it has a light-sensitive emulsion spread on top. This emulsion contains silver halide crystals that are suspended in gelatin. When you take a photograph, the light is focused through the lens of the camera onto the camera film. For a color photograph, there are three layers of emulsion, and each one has particles that are sensitive to a different wavelength of light. The film has to be kept in the camera or in its case or in a dark room because it is very sensitive to light and any exposure to daylight would destroy the film.
When it is developed, the film is unrolled in a dark room or in a machine and passed through a bath of chemicals. The silver halide crystals in the film are altered by the amount of light they received. In the chemical bath, these crystals can be converted into metallic silver, and the more light they received originally, the darker they will be. That is why camera films are produced as a negative. In color film, colored dyes attach to the metallic silver, and this also corresponds to the amount of light they originally received. Late,r the image is printed onto photographic paper. This is how a color photograph is usually produced.
Polaroid cameras do all of this, but inside the camera, and very quickly. Each Polaroid is loaded with instant photo film, which can be used for a single picture. The film is made of several layers. The bottom layer is a black base layer. On top of this are different dye layers, which will be used to make the colors. Then there is a light sensitive layer on the top. When you take a picture, the lens focuses the light onto the photo plate, just like in a regular camera. After you have taken the picture, the camera ejects the photo plate, and this is where the magic happens. If the plate is just ejected, the picture will be ruined by the daylight, so the camera needs to protect the image. At the edge of the photo plate, in a line along one side, is a chemical reagent. As the photo is ejected from the camera, it goes through a roller that squeezes the reagent and spreads it over the light sensitive layer. The reagent spreads over the layer that becomes the picture and under a layer of acid, separated by a timing layer. The reagent contains opacifiers, which block out the light and protect the image underneath. The reagent also contains chemicals that start to develop the picture. The chemicals in the reagent seep down through the layers in the photo plate, and they turn the activated silver halide crystals into metallic silver. Then the chemicals start to dissolve the dye layers, and when this happens, the dye begins to rise to the surface. Where there is no metallic silver, the dye rises right to the top, but where there is metallic silver, the dye attaches to it. All of the dyes that weren’t grabbed rise to the top and make a layer underneath the reagent. Finally, the timing layer above the reagent dissolves, and the reagent comes into contact with the acid layer. This neutralizes the reagent and dissolves any leftover dye, and the picture becomes clearer. When we wait for a Polaroid picture to become clear, we are not waiting for the image to develop; we are waiting for the opaque layer to dissolve. The image has already developed underneath it. And when we test to see if a Polaroid has dried, we are not testing to see if ink has dried, but testing to see if the reagent layer has dried.
The Polaroid camera was invented by an American inventor called Edwin Land. The story is that he was on vacation with his small daughter. He took a photograph of her, and she asked why she couldn’t see it straightaway. That got him thinking, and within three years, he had invented the instant camera. He started the Polaroid company, and it was hugely successful until the invention of digital cameras put it out of business. Then, with smartphones, it became completely unnecessary. However, since 2017, there has been a revival, and there is more interest in Polaroids and instant photos. Polaroids are seen as cool and retro, but technology is still moving on. You can buy tiny handheld printers that connect to your phone via Bluetooth so you can print out any picture, wherever you are. The quality is better than a Polaroid, and you can choose the picture before you print it. Polaroid, among other companies, is a producer of these printers. Still, there is something about using a Polaroid that is lost when you use a printer. And this is what I learned today.
Sources
https://science.howstuffworks.com/innovation/everyday-innovations/instant-film.htm
https://en.wikipedia.org/wiki/Instant_film
https://en.wikipedia.org/wiki/Polaroid_Corporation
https://en.wikipedia.org/wiki/Edwin_H._Land
https://en.wikipedia.org/wiki/Photographic_film
https://en.wikipedia.org/wiki/Silver_halide
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