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Understanding the Resolution of Digital Images What is the resolution of an image of archival "quality" ? To qualify archival images, who will use them and how (in what type of media or technology) they will be used must be predict. The progress of these media and technologies must be also anticipated to allow them to be still usable in the longer term, without having to rescan them again. However, there are also constraints to their preservation, including the purchase and maintenance of storage of master files and backup copies on secure media. The level of resolution for archival images should then, at least, provide the best possible flexibility of use and impose the fewest possible restrictions. As the quality of an image depends on the quantity of pixels captured and their density, these two factors then must be consider determining the best level of "quality". So it is not recommended to focus only on the density of images, by scanning them all at the same resolution (eg 600 dpi), without considering also the size of the original documents. Rather, it is recommended to scan images at resolutions adapted to the original's dimensions, to obtain digital copies of standard dimensions. It is generally considered, in digital preservation, as images containing 3000 pixels on their longest side, offer enough flexibility for various uses, without generating too large electronic files (about 20 Megs). With advances in technology and lower cost to buy it, these standards can even be doubled (6000 px longest side), but the generated image files are then larger (about 80 Megs). In general, scanning at a minimum of 3000 px (longest side) is sufficient when the originals are common, recent and in good condition. Digital copies produced allow 8 x 10 prints at 300 dpi. However, if the originals are rare, old or fragile, it may be better to scan at 6000 px (longest side). This captures in one shot, a maximum of information, and avoids handling them again in the short term. The "performance" of the equipment shall not affect the level of desired "quality", but may still be considered for their potential to facilitate the processing of different types of originals. Whatever the chosen standard, this approach also has the advantage to facilitate the calculation of required space to store images (ex: 100 files @ 20 Megs = 2 gigs). Community Digitization Program of Prescott-Russell 3