Minilab

A minilab is a small photographic developing and printing system, as opposed to large centralized photo developing labs. Many retail stores use minilabs (or digital minilabs) to provide on-site photo finishing services.

With the increase in popularity of digital photography, the demand for film development has decreased. This means that the larger labs capable of processing 30 or 40 thousand films a day are going out of business, and more retailers are installing minilabs.

In Kodak and Agfa minilabs films are processed using C41b chemistry and the paper is processed using RA-4. Using these chemical processes films can be ready for collection in as little as 20 minutes, depending on the machine capabilities and the operator.

A typical minilab consists of two machines, a film processor and a paper printer/processor. In some installations, these two components are integrated into a single machine. In addition, some digital minilabs are also equipped with photo ordering kiosks.

35 mm films are pulled, this means the end of the film is extracted from cassette. This can be done manually or by using a small machine that essentially uses tape to pull the film leader out of the cassette. In cases when the end of the film cannot be removed or if the film is damaged, the film can be removed using a dark bag or a dark box. A twin check number (a pair of stickers with a unique number) is put onto the film and the matching number onto the film processing envelope, so that after processing this film can be easily identified to the customers envelope. Films are spliced on the leader cards one or two at a time, to do this the end of the film is cut square, special chemical resistant tape is used to attach the film to the leader card. The leader card(s) is/are then inserted into the film processor and are fed through the machine using sprockets in the card. The film goes through a developer, bleach, fix and stabilizer then through a dryer. After the film is processed it is cut from the leader card and re-united with the processing envelope containing the customer details, from here the film goes forward for printing.

A minilab is typically a continuous loop processor, where the film follows a serpentine path over many rollers. Each chemical processing step is done using a chemical immersion tank with recirculation to keep the fluid evenly mixed. Film advances down into the tank and then turns and rises up and out, then advances down into the next tank, and so forth. Chemical exposure timing is a combination of film advance speed and the physical length of the serpentine film path immersed in the fluid.

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Wikipedia