Digital images: vector and raster

Digital images are most commonly one of two sorts: raster images and vector images. Raster images describe the location and colour of pixels in an image file and create images such as photographs or scans. By contrast, vector images are based on mathematical instructions and lend themselves to defined lines, curves, shapes, logos, fonts and technical drawings.

The Modern Records Centre recommends the use of uncompressed TIFF for your origin copy raster images (eg when digitising content) and either JPEG or PNG as your delivery raster format (eg for sharing on the internet). We recommend the use of SVG as your origin copy and delivery vector image format.

Images taken with a digital camera (raster) can be exported in few ways; as the RAW data file, an in-camera processed TIFF or as an in-camera processed JPEG file. The RAW format generated by a digital camera is proprietary to the camera manufacturer. Tagged Image File Format (.tif) will either be uncompressed or compressed. An uncompressed TIFF will retain the original detail but because it has received in-camera processing it will not retain the exact data as captured by the light sensitive chip. A compressed TIFF will sacrifice detail as a result of the compression process.

Joint Photographic Experts Group JPEG Interchange Format File (lossy compression) (.jpg) is a compressed file which has undergone lossy compression. This means that detail will have been sacrificed during the compression process. You will be able to convert a JPEG to a TIFF but you will not retrieve the data sacrificed during the JPEG compression process.

You can get more in depth information about vectorLink opens in a new window and raster images from the Archaeological Data Service