Offset printing is a commonly used printing technique where the inked image is transferred (or “offset”) from a plate to a rubber blanket, then to the printing surface. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a water-based film (called “fountain solution”), keeping the non-printing areas ink-free.
Digital printing refers to methods of printing from a digital based image directly to a variety of media. It usually refers to professional printing where small run jobs from desktop publishing and other digital sources are printed using large format and/or high volume laser or inkjet printers. Digital printing has a higher cost per page than more traditional offset printing methods but this price is usually offset by the cost saving in avoiding all the technical steps in between needed to make printing plates. It also allows for on demand printing, short turn around, and even a modification of the image (variable data) with each impression. The savings in labor and ever increasing capability of digital presses means digital printing is reaching a point where it will match or supersede offset printing technologies ability to produce larger print runs at a low price.
Large format describes large photographic films, large cameras, view cameras (including pinhole cameras) and processes that use a film or digital sensor, generally 4 x 5 inches (10×13 cm) or larger. The most common large formats are 4×5 and 8×10 inches (20×25 cm). Less common formats include quarter-plate, 5×7 inches, 11×14 inches, 16×20 inches, 20×24 inches, various panoramic or “banquet” formats (such as 4×10 and 8×20 inches), as well as metric formats, including 9×12 cm, 10×13 cm, and 13×18 cm.
The Polaroid 20×24 inch instant camera is one of the largest format cameras currently in common usage, and can be hired from Polaroid agents in various countries. Many well-known photographers have used the 235 pound (106 kg), wheeled-chassis Polaroid.
The term of art “Large Format” refers to film and camera formats that generally use sheet film in sizes equal to or larger than 4 inches by 5 inches (or 9×12 cm). (Although there are some view cameras in sizes smaller than 4×5 inches, or 6x9cm). Large Format distinguishes large cameras 4×5, 5×7, 4×10 and 8 x10 inches, from medium format cameras and film (6×6, 6×7, 6×8, 6x9cm roll film cameras) and from small format cameras of 35mm, 110 and smaller film sizes. Above 8×10 inches, the formats are often referred to as Ultra Large Format (ULF) and may be 11×14, 16×20, 20×24 inches, or as large as film, plates or cameras are available.