LPedia:Document Scanning Guidelines

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Many historical documents were originally made available only in printed form. This includes almost all newsletters prior to this century. Other documents, while they may have originally been produced using a computer, were only widely distributed in hardcopy form, and the original computer files are no longer available. There are also some documents for which the "original" was inherently hardcopy, e.g., personal handwritten correspondence or letters written using a typewriter.

In all of these cases, to make the documents available through LPedia the first essential step will be some kind of scanning. This article provides guidelines and suggestions for doing that scanning in ways that will be most helpful both for current viewing and for future use.

General Principles

  • Use the best "original" available.
  • Higher resolution is better.
  • If the original contains any sort of color, do a color scan if possible
  • Keep track of what you are doing -- label resulting files consistently.

Minimum Resolution

The appropriate scanning resolution will vary according to the type of material, and will also necessarily be influenced by the scanning equipment available. If a document can only be scanned in circumstances where limited scanning facilities are available (e.g. a portable scanner or in some cases perhaps just a phone or pocket camera), that's still better than nothing! But in most cases the minimum resolution should be determined by whatever is necessary to capture all of the essential features of the text or image(s) and which allows for display that doesn't look "fuzzy" to the unaided eye.

For ordinary printed text, resolution should be at least 600dpi.

For photographs, the size of the original can vary widely, so it's the total number of pixels that is the important thing. The resulting file should be at least 6 megapixels. For a 3.5 x 5 in. photo this would correspond to a scanning resolution of about 600dpi. When scanning a large print (e.g., 8x10 in.) a lower scanning resolution might be appropriate; for a 35mm slide it would be significantly higher.

But don't be afraid of scanning at higher resolutions, if the appropriate equipment is available. It's easy to reduce the resolution after the fact, to produce alternate versions that can be stored or transmitted more easily. It's impossible to create additional resolution later without re-scanning -- which if something happens to the original may turn out to be never.