Scanners, the most popular image capture device for creating digital images, can be used with existing photographic materials such as slides, photographs and transparencies; they can also be used to digitise original two-dimensional objects or flat materials such as documents, prints and drawings. Over the last few years, scanners have greatly decreased in cost and increased in functionality, which means that they are no longer the specialty item they once were. Scanners have become almost as common as printers and as easy to use: Manufacturers now offer one-touch scanning.

Careful consideration must be made when selecting a scanner to ensure that the equipment choice meets the digitisation needs of your institution when capturing images for long-term archival purposes

The wide range of scanner types and models available can capture a variety of formats or objects.

A flatbed scanner, sometimes called a reflective scanner, is what most people first think of when they consider scanners; it is the most common and most versatile of all scanners on the market today. A flatbed scanner, which resembles a copying machine, can effectively scan any two-dimensional flat artwork, photographs, drawings, books, paper and near-flat three-dimensional objects.

Flatbed scanners can be adapted to scan film transparencies such as 35 mm film by adding an optional transparent media adapter (TMA) unit that is usually mounted on top of the flatbed scanner in place of the standard cover. This device shines a bright light from above through the film to the image sensor below. The slides or negatives are then placed on the glass plate in an appropriate frame, illuminated from above, and scanned. Because of the small size of the originals, the resolution rendered by a flatbed scanner is usually lower than a film scanner, which results in a lower quality image. A dedicated film scanner would be a better option for scanning large numbers of 35mm slides or other transparencies.

A sheetfed scanner resembles a fax machine more than a copier, since it moves the page being scanned past the scanning head instead leaving the material stationary. Generally used for optical character recognition (OCR) or text scanning, they are not as exact as flatbed scanners because of the difficulty of moving a sheet of paper without introducing distortions. An option for the sheetfed scanner is an automatic sheet feeder to batch-process large quantities of paper.

A film scanner, most commonly referred to as a slide or transparency scanner, is specifically designed for scanning transparent film-based materials such as 35mm slides or negatives. Some of the higher end film scanners can also handle medium (4" x 5") or large-format film or transparencies. These scanners work by passing a light through the film rather than reflecting light off it. Because of their small size, slides need to be scanned at a very high resolution. Film scanners are generally more expensive than flatbed scanners and are less versatile. An option for the 35mm slide scanners is an automatic slide feeder for batch processing.

A combination scanner combines the transparency scanner and flatbed scanner in one unit. In addition to the usual glass plate for reflective objects, these scanners also have a separate built-in unit or drawer for inserting the film which can be scanned at high resolution.

Drum scanners are mainly used by scanning bureaus for high-quality professional layout scanning. The original image is mounted on a round cylinder or drum, which then spins around a central recording mechanism. With each pass the scan becomes more refined, resulting a very-high-quality image. Drum scanners are very expensive, but offer features not available to desktop scanners, such as direct conversion to CMYK, auto sharpening, greater dynamic range, and large image scanning areas.

Handheld scanners, which come in a variety of shapes, capture images when the scanner is passed over the original material. They require a very steady hand to operate and tend to do a poor job in capturing colour. Although still the cheapest, they are rapidly being replaced by low-cost flatbed scanners. Handheld scanners should not be considered for capturing high quality images.

The quality of the scanner is depends on its optical components and features, which in turn drive the cost of the scanner. You can perform tests or consult reviews done on scanners to compare the output quality. Some of the terms related to quality are:

Noise is electronic interference that can cause inaccuracies in images. In scanners, this noise has its greatest effect in low-light-level detection, i.e., when scanning the dark areas of images. Higher quality 30- or 36-bit scanners can give better results, as they tend to use higher quality (lower-noise) components.

Resolving power is a function not only of the optical resolution, but also the quality of the scanner's optical system, the stability of the transport mechanism, the type of sensing elements used, and other design factors. A high-quality scanner may have significantly more resolving power than a lower quality scanner of the same optical resolution.

Colour registration is the ability of the scanner's image sensor to precisely register the red, green and blue planes during the scan of a colour image, which is done at high speed. Proper alignment is necessary to produce clean colours.