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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 sticker 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.
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.
Most printer/processes are computer controlled. The front of the film is fed into the printing gate. Sensors see the film and forward the film to the first frame. DX codes on the edge of the film are read by the printer and the film channel is selected accordingly to give the optimum result.
The paper stock is usually a continuous roll which cut after developing according to the size requirements of the customer. Different image widths are handled using different roll widths, and each width is usually done as a batch process of images all the same size. The light-sensitive paper stock can be contained within light-tight packaging so that the minilab operator only needs to remove the old empty paper container and insert a full one, without needing to darken the room to prevent paper exposure.
Each frame is printed one at a time, the photographic paper is advanced each time and when there is sufficient frames printed the paper automatically advances into the paper processor. The paper passes through a developer, bleach/fix, a wash, and dryer. The prints are then cut up and are collected in a bundle. From here a smaller machine is used to cut the negatives into fours and sleeved to protect them.
The final job is to put the negatives with the prints into a wallet and into the processing envelope. The order is then priced and placed into a rack or draw waiting for the customer to collect.
By the end of 2005, two manufacturers, Agfa and Konica went out of business. Minilab Factory GmbH took over the renowned minilab branch of Agfa in 2006. Gretag Imaging, not to be confused with former Gretag Macbeth, went bankrupt in December, 2002. Subsequently, the minilab related assets were sold to the newly formed San Marco Imaging. The wholesale lab related assets were sold to KIS Photo Me Group. In 2006, Noritsu and Fuji announced a strategic alliance. Noritsu now manufactures all of Fuji's minilab equipment 
A digital minilab is a computer printer that uses traditional chemical photographic processes to make prints from digital images. Photographs are input to the digital minilab using a built-in film scanner that captures images from negative and positive photographic films (including mounted slides), flatbed scanners, a kiosk that accepts CD-ROMs or memory cards from a digital camera, or a website that accepts uploads. The operator can make many corrections such as brightness or color saturation, contrast, scene lighting color correction, sharpness and cropping. A laser, LCD/LED, or Micro Light Valve Array (MLVA) then exposes photographic paper with the image, which is then processed by the minilab just as if it had been exposed from a negative.
The price of a digital minilab can reach up to $250,000 USD. A minilab, such as a Doli DL 1210 has a print resolution of 520dpi, accepts BMP, JPEG, and TIFF formats, and can print up to 8in by 12in. The most popular brands include KIS, Noritsu, Doli and Fuji..
Digital minilabs are generally too expensive for typical home use, but many retailers purchase or lease them to offer photo printing services to their customers. The resulting photographs have the same quality and durability as traditional photographs since the same chemical processes (e.g. RA-4) are used. This is often better than can be achieved by typical home inkjet printers, and for smaller prints generally less expensive.
A new type of minilab is the dry lab, which does not require the use of developer or fixer chemicals, and does not require moistening and then drying of the print. These machines are cheaper, smaller, and use inkjet printing instead of a chemical developing process. This allows them to be installed in smaller retail stores, print shops, and resort/tourist locations that could not justify an expensive, high throughput, wet minilab. Standard questions of inkjet quality and longevity apply.
"Dry lab" is a term that evolved in the professional and consumer segments of the photo printing industry to distinguish later, chemistry free (or "dry") photo printing systems from traditional, silver halide (or "wet") systems.
There are currently two technologies used by manufacturers as print engines for either professional or commercial "dry labs". Although not strictly "dry", the first technology is a dye based, four colour (Yellow, Cyan, Magenta & Black) inkjet system. Inkjet based dry labs output prints with a relatively wide colour gamut although colours may take a few hours to stabilise after printing while the ink fully dries. The second technology that can be used is "dye diffusion thermal transfer" or D2T2 technology. D2T2 is a three colour (Yellow, Cyan & Magenta) thermal process whereby the colour dyes are transferred from an ink ribbon onto, or rather into, the surface of a special paper substrate. "Dry labs" are becoming increasingly popular with users as they are cheaper and easier to maintain than wet labs.
- FUJIFILM Global | About Fujifilm | News Releases
- ImagingInfo.com - Article - Do Fuji and Noritsu Look Alike? Reason: They Really Are (Well, Almost)
- http://www.doli.com.cn/download/online/en/1210%20Service%20Manual.pdf | Doli DL1210 Operation Manual, page 15
- NewPhotoDigest | Dry minilabs are in demand