A digital camera back is a device that attaches to the back of a camera in place of the traditional negative film holder and contains an electronic image sensor. This lets cameras that were designed to use film take digital photographs. These camera backs are generally expensive by consumer standards (US$5,000 and up) and are primarily built to be attached on medium- and large-format cameras used by professional photographers. Types Two sensor back types are commonly used: single shot back (non-scanning) and scan back. Some backs, primarily older ones, require multiple exposures to capture an image; generally one each for red, green, and blue. These are called multi-shot or 3-shot backs. As technology advanced single-shot backs became more practical; by 2008 most backs manufactured were single-shot. Early backs had to be used tethered by a cable to a controlling computer that would store the images they took. Newer models added the ability to store the photos inside the back itself, and added displays so that the picture could be viewed on the back without requiring a separate computer. Virtually all backs can still be operated in tethered fashion, which allows convenient previewing of images on a large monitor by several people at the same time, sophisticated control of camera functions, and convenient storage for the large image files produced. Modern high resolution backs that push the limits of data storage and transfer technology still are able to make use of a tethered configuration to offload gigabytes of data to cheaper external storage mediums such as hard drives, instead of the more expensive integrated flash memory. Single shot back Non-scanning backs have a sensor similar to that used in most other digital cameras, a square or rectangular array of pixels. Backs are generally assumed to be non-scanning unless specified to be a scan back. Scan back Scanning backs operate more like an image scanner for paper: they have a linear array of sensors that is moved across the image area to scan the image one row of pixels at a time. Scanning backs are primarily used in large format view cameras. History The first commercial digital camera back was introduced by Leaf (now part of Phase One) in 1991. The Leaf DCBI (Digital Camera Back I), nicknamed "The Brick", offered resolution of 4 megapixels (MP) in a 2048 × 2048 pixel format. The same CCD was used by Sinar in its