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Digital images

We can provide digital images on CD at a choice of two different standards.

  • Standard digital image

    This is a medium size file for reproduction of smaller items such as engravings from books or details from manuscripts. It is not recommended for high-quality or large reproductions, or indeed large items such as maps.

  • Premium digital image

    This is a large file size suitable for items or maps that have fine detail.

DPI (Dots per inch) and Resolution

We have standardised on 300dpi for direct image capture, and any smaller dpi that is supplied will have been converted from our 300dpi standard. This will not change the image in any way, it only affects the small data file that holds information about the image and is tagged onto the file.

The colour depth that we use is 24 bits, and the colour space is RGB. This gives an idea of how much information the files contain. It is similar to film sizes. The larger more expensive film sizes hold more information than the smaller formats and the same applies to larger or smaller file sizes. NB: It is sometimes difficult to be precise about the file sizes because the books, maps, manuscripts etc. are different shapes. For example a square item photographed to the same standard as a rectangular one will give different file sizes.