Scanner Resolution: DPI Explained and How Much You Need

What Is DPI?

DPI stands for dots per inch and measures the level of detail a scanner captures. Higher DPI settings capture more detail but produce larger file sizes. Understanding the right DPI for your needs prevents unnecessary storage waste while ensuring adequate quality.

Optical vs. Interpolated Resolution

Optical resolution is the true resolution of the scanner's sensor. Interpolated resolution uses software to artificially increase the apparent detail. Always compare optical resolution values when evaluating scanners, as interpolated resolution does not add genuine detail.

Recommended Resolution by Use Case

For standard business documents, 300 DPI provides clear, readable scans. For photographs intended for reprinting, 600 DPI captures sufficient detail. For archival purposes or images that may be enlarged significantly, 1200 DPI or higher ensures maximum detail preservation.

File Size Considerations

A 300 DPI scan of a letter-size page produces a file of roughly 25 megabytes in uncompressed format. At 600 DPI, the file size quadruples. Use compression formats like PDF or JPEG to manage storage requirements without significant quality loss for most purposes.

Colour Depth

Scanner colour depth, measured in bits, determines how many distinct colours the scanner can capture. Most scanners offer 24-bit colour for standard use and 48-bit colour for professional photography and archival work.