Most digital cameras are designed to function as a self-contained unit. Those models at the lower-end are especially so for these cameras typically include zoom lens and flashes that cannot be adjusted. Those cameras at the highest-end however, are a sophisticated light-sensing unit. Seasoned photographers attach these digital “camera backs” to their professional medium format SLR cameras, such as a Mamiya.

Scanning and multi-shot camera backs are usually used only in studios to take photos of still objects. Most of the earlier, primitive digital camera backs used linear array sensors taking seconds or even minutes for a complete high-resolution scan. The linear array sensor acts like its counterpart in a flatbed image scanner by moving vertically to digitize the image.

Many early cameras could only capture grayscale images. To take a color picture, three separate scans done with a rotating colored filter were required. These are called multi-shot backs. Some other camera backs use CCD arrays similar to typical cameras. These are called single-shot backs.

Cameras with a digital sensor smaller than the typical 35mm film size will have a reduced field or angle of view when combined with a lens of the same focal length. This is basically due to the angle of view being a function of both focal length and the sensor or film size utilized. If a sensor smaller than the full-frame 35mm film format is used, such as the use of APS-C-sized digital sensors in DSLRs, then the field of view is cropped by the sensor to smaller than the 35mm full-frame format’s field of view.

This narrowing of the field of view is often described in terms of a focal length multiplier or crop factor, a factor by which a longer focal length lens would be needed to get the same field of view on a full-frame camera. If the digital sensor has approximately the same resolution (effective pixels per unit area) as the 35mm film surface (24 x 36 mm), then the result is similar to taking the image from the film camera and cutting it down (cropping) to the size of the sensor. For an APS-C size sensor, this would be a decrease to roughly the center 50% of the image. The less expensive, non-SLR models of digital cameras typically use much smaller sensor sizes and the reduction would be greater.