Color Depth

Color depth (also called bit depth) measures how much color information a digitized image holds per pixel, expressed in bits. A 1-bit image stores only black or white; 8-bit grayscale captures 256 shades of gray; and 24-bit color reproduces roughly 16.7 million colors. Higher bit depth yields more faithful tonal and color reproduction at the cost of larger file sizes.

In recordkeeping, color depth is a core imaging specification that helps determine whether a digital surrogate adequately captures the informational and evidential content of an original record. Documents bearing color seals, signatures, highlighting, or photographs may require higher color depth to remain authentic and usable, while routine text may be acceptable in grayscale or bitonal form. Capturing color depth as technical metadata supports long-term preservation and migration decisions.

For example, a scanning specification might require 24-bit color at a set resolution for permanent records destined for archival transfer, ensuring the surrogate meets accepted digitization standards and preserves visual evidence that bitonal scanning would discard.