How it works: instant film

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Joel Fulleda
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How It Works: Instant Film Romane Riesse, Digital Focus (@Lesnums) Posted on 19/04/18 at 14:00 Share:

Enjoying her photos immediately: such was the wish of a little girl in the 1940s for whom her father developed treasures of ingenuity in order to conceive what was to become generically instant photography. Let's climb back into the time machine...

One of the first instant films sold by Polaroid.

Originally in sepia and black and white

In its infancy, instant photography did not yet have the form that we know of it today. Originally designed in sepia (Type 40) and then black and white (Type 41), Polaroid's instant photography is a roll film system called Peel-Apart, a film that combines a negative and a positive stored on two independent reels housed inside the camera.

Once exposed, the positive/negative assembly is extracted from the device, then pressed and crushed between two rollers. The system makes it possible to crush and evenly distribute the chemical components included in a tank located between the two surfaces of the negative and the positive. The final photograph then appears on the positive after separation from the negative. Polaroid will develop 18 types of roll film from 1948 to 1992, with a variation in a sheet film system for professionals using cameras in 4x5 and 8x10 formats.

The system will follow film pack (1963) popularized with the Type 100. The concept is both simple and ingenious: a box contains 10 photos whose negative/positive/chemistry sets are separated by a spring and tabs. Development is done by first pulling the white tab which places the exposed negative in front of the image-receiving positive sheet. You then have to pull on a second tab (yellow), attached to the chemistry, which passes the sandwich between the two pressure rollers, then outside the device, spreading the chemistry between the negative and the positive and launching the development process. The action of the chemistry finished (a few minutes…), it suffices to separate the positive from the negative to reveal the final image.

Illustration from one of Polaroid's patents.

Appeared with the Polaroid SX 70 camera and popularized with the Polaroid 60, the instant process with development Integral is arguably the most famous instant film of all. Square and edged in white (78 x 80 mm in a usable format of 89 x 108 mm), the Integral film inherits the “sealed box” concept of the Filmpack, but this time requires no user intervention for its development. The photos obtained are of hard surface, they remain sealed on the support from which they are inseparable. This time there is no waste, nothing to separate, unlike the Filmpack. The final image is ejected and develops on its own, without duration control.

The color image is practically formed in 4 min. The Polaroid Integral film, with a sensitivity of the order of ISO 100, consists of two main elements: the negative and the positive. Metallic dyes are contained in the negative which will migrate into the positive during development to form the color image. On one side of the film is the flat capsule containing the three chemical agents (alkaline solution, opacifier, titanium dioxide) necessary for development. Intimately linked, negative and positive will never be separated. The exposure of the film is carried out through the positive film which is completely transparent at the time of exposure, which explains the presence of the mirror inside the cameras using this film. When the frame is taken, the film is driven by the motor of the camera and ejected passing through the two pressure rollers so that the chemical agents are spread.

At the same time, Kodak launched its PR 10 packaged in 10 views on the same principle of sealed Integral development. The images are this time rectangular on a support with white margin of 97 x 102 mm for a useful surface of 68 x 91 mm. Intended for Kodak EK-2 and EK-8 (mirrorless) and EK-200 and EK-300 (dual mirror) instant cameras, PR 10 film is exposed from the backside of the negative so that the positive image is seen in common sense, unlike the process of Polaroid exposed through the positive film. Each film consists of a backside (exposure side), an image forming and receiving area, a capsule containing the chemicals, and a trap to absorb excess developer.

Compared to that of Polaroid film, the capsule is on the horizontal edge of the format, where the white margin is the widest. The trap is located on the opposite edge. The imaging zone is between the capsule and the trap. When the photo is taken, it passes between the pressure rollers crushing the capsule and spreading the developer in a very thin layer between the negative and the positive. The backing is a polyester film (Estar) coated with a layer that prevents the print from bending. The other side is coated with a layer of acid and layers of retarders. During processing, the developer penetrates and develops the emulsified layers of the image forming area. The acidic layer then neutralizes the highly alkaline developer coated on the exposed surface of the imaging area. The retarder layers then control the development time of the film.

Today's Polaroid

After its liquidation in February 2008, Polaroid was reborn from its ashes under the impetus of a few former chemical engineers who ended up buying the Enschede factory in the Netherlands. Under the trade name The Impossible Project, the team of chemists is redeveloping two new instant films of the Integral type, compatible with the SX-70 and 600 systems, taking care to comply with the new European legislation concerning the use chemical products. They therefore had to start from scratch with the development of the PX100 and PX600 films, marketed at the beginning of 2010. Films that were very unstable in their early days with very random color renderings, but which gave hope to fans of the famous square format. In 2017, Impossible metamorphosed and reappeared under the name Polaroid Originals with, in its catalog, a range of films of the Integral type for the SX-70, Polaroid 600 and Spectra, as well as films for large format 8x10 cameras. The firm remains very discreet about the formulation of the chemical components of its films, adapted to European standards while using the same concepts of the film with Integral development presented in… 1972!

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5 years ago

Fujifilm Instax

Fuji is now one of the major players in instant photography with the Instax film range well established among users. The snapshot revisited by Fuji dates back to the early 1980s during which the firm produced its first instant cameras and integral films, the fruit of negotiations with Kodak, then a competitor of Polaroid. Fuji develops the F Series films, then very close to the technology used by Polaroid. Today, the Instax process is similar to those pioneered by Polaroid and Kodak, but closer to Kodak's with exposure from below through the positive film. With a thickness of 10 µm, the film has 18 photosensitive layers. It integrates an image receiving layer, a developing layer as well as a developing layer used for image exposure, development and formation. At the center of a vast ecosystem, Instax films now exist in a color version in rectangular (mini, large) or square format, as well as in a monochrome version in mini format.

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