Group blog post - „How pictures are developed“

Each day photo laboratories receives many rolls of film for development. To process each exposure it is first turned into a negative image and then into a positive one. That positive image is what is known as a photograph. First, a scanner takes the envelopes which contain the film and sorts them into bins, according to what size the final picture should have and according to how many copies need to be made of each picture. Then, a machine extracts the film rolls from the metal capsules in total darkness. Exposing the film to light would ruin the photo because the film is sensitive to all of the visible wavelengths of light and photons emitted from the light source change the chemical nature of the particles the film is made of. The envelopes from the bins are then transferred into bundles so they can later be reunited with the right pictures and negatives. From the inside of the machine a blade cuts open the metal capsules. The machine unravels and lines up films as long as sixty meters. A sticker is being placed on the films in order to identify each film with a barcode. Once the machine measures the assembled strip, which gets wrapped onto a wheel inside a metal box. Developing the exposures requires four chemical baths in complete darkness. In the first chemical bath, sulfates make the image appear as a negative. The second chemical bath includes acetic acid to hold the effects of the sulfates. The last two baths preserve the image and rinse away any chemical traces. To print pictures the negatives are loaded into yet another machine which contains light sensitive paper. All it takes is a flash to transfer the image. A sensor instantly adjusts the intensity to correct any improper exposure by the photographer. To develop the prints the paper now goes through four chemical baths similar to those used for the negatives before.

One chemical bath reveals the image and another chemical bath stops that process. Two more chemical baths preserve the image and rinse off the chemicals. This time, however, the paper goes into an oven to dry for two minutes at seventy degrees Celsius. Then, a technician marks the pictures that are too bright, too dim or out of focus and removes them from redeveloping. Next, a machine unwinds the strip, scans the barcodes and cuts out the pictures that belong together. It also cuts the negatives into numbered strips of four. Once this is done, the photos and negatives are slipped into an envelope. The computer shows just what to include in each envelope and a machine provides the film’s original package which is also included in the envelope. Now the owner can sit back and enjoy his/her pictures.