Imaging Guidelines

These guidelines apply to materials digitized by the UNH Library Digital Collections Initiative or by library departments for inclusion in the UNH Digital Collections.

While it is not possible to capture every physical nuance of materials or to anticipate all possible future uses, it is recommended to image (scan or digitally photograph) at sufficient quality to support the primary functionality of the original material, to be flexible for display, viewing, and printing, and to prevent the need to re-image materials for the foreseeable future.

Imaging Guidelines

Format of original Color Parameters Sampling Resolution
Accepted Recommended Accepted Recommended
Printed text/simple line art Bitonal (2 bit) Grayscale (8 or 16 bit) or Color (24 or 48 bit) 300 ppi 400-600 ppi
Manuscripts, hand-drawn illustration, typewritten, or low-contrast printing. Grayscale (8 or 16 bit) Color (24 or 48 bit) 300 ppi 400-600 ppi
Halftones/screen printed images Grayscale (8 or 16 bit) Color (24 or 48 bit) 300 ppi 400-600 ppi
Continuous tone images (printed photographs, fine line art). Grayscale (8 or 16 bit) Color (24 or 36 bit) 400 ppi 600 ppi
Cartographic materials (oversized) Color (24 bit) Color (48 bit) 300 ppi 400-600 ppi
Transmissive materials (transparencies or negatives on any type of support) Color (24 bit) Color (48 bit) 3000 pixels on the longest edge 4000-6000 pixels on the longest edge

Accepted is the minimum quality that will be considered and should seen as a starting point for determining the specifications for a given project – size of text, amount of detail, and complexity should be taken into account. It is recommended that a representative sample of the collection be imaged at various settings to determine minimum requirements for accurately rendering the smallest meaningful detail in the original.

Recommended is a known optimal imaging range for balancing quality with file size manageability for typical materials, but files of higher quality resolution and bit depth are acceptable and maybe necessary for original document with very fine details or a high level of clarity.


  • When imaging halftone or other screen-printed images, image at a high enough resolution to prevent visible moiré patterns.
  • Although bitonal and/or grayscale color spaces are given as options, color imaging is required when meaningful color is present in the original – meaningful means necessary for understanding and interpreting material, or contributing to aesthetic intent.
  • Originals – it is acceptable to image a surrogate, e.g. print of a photographic negative, if the original is unavailable or may be damaged by the imaging process. Materials that cannot safely withstand currently available imaging processes should not be selected for digitization.