Minilab

A minilab is a small photographic developing and printing system or machine, as opposed to large centralized photo developing labs. Many retail stores use film 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 30,000-40,000 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. With 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. Despite their small size, minilab machines may use chemical processing just like larger dedicated photo processing labs, using processes such as CP-49E or RA-4 for photographic paper processing, and C-41 for film processing. All necessary processing chemicals may arrive in a box (replenishment cartridge) containing enough bleach, developer and fixing agents to be mixed automatically for an estimated amount of paper, eliminating the need to manually handle and mix chemicals. Minilab machines were used in stores to perform film processing and printing in a short period of time, usually less than one hour from start of film development to the end of printing, partly because it eliminated the need to send rolls of film and printed photos to and from a large central photo processing lab.

Film processor 35 mm films are pulled, this means all of the film is extracted from its roll. This can be done manually or by using a small machine that essentially uses tape to pull the film leader and all of the film out of the cassette. This small machine may be integrated into the film processor. If so, rolls are inserted inside a chamber, slot side towards the inside of the machine pointing downwards at an angle of 45°, the chamber is closed and the film inside the rolls is pulled into the processing mechanism. 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. Before processing, a twin check number (a pair of stickers with a unique number) is manually 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 customer's 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 cards are then inserted into the film processor mechanism 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 reunited with the processing envelope containing the customer details, and then from here the film goes forward for printing. Alternatively the film may be used immediately to expose silver halide photographic paper, shining a bright light through the film and into the paper using lenses for optical enlarging, which is then processed like film in a separate mechanism. Or the film may be digitally scanned using a CCD image sensor, corrected using software, and sent to a digital silver halide printer. A minilab is typically a roller transport processor, where the film follows a serpentine path over many rollers. Each chemical processing step is done using a chemical immersion tank with replenishment to keep the chemicals fresh. 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. The fluid in the tanks is usually agitated, filtered and warmed to 100 °F (necessary for the C-41 process), and the fluid also needs periodic replacement. The Film processor also has a dryer, just like wet silver halide printers. A single minilab can be built to allow many different film widths in one device, from APS films to professional wide format films, using a flexible leader to pull the film through the mechanism. The leader is as wide as the widest possible format, and films attached to it are supported by guide rollers only. The leader may be gripped on each side between toothed drive belts following the same path as the film through the mechanism. An example of a film processor minilab is the Noritsu QSF series of machines.

Photo printer

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