Bit depth

Bit depth is the number of bits a system allocates to store the tonal value of each colour channel per pixel — the count directly sets how many discrete tonal steps or shades are available between pure black and pure white (or between the darkest and lightest value of a channel). Common depths are 8-bit, offering 256 levels per channel, and 16-bit, offering 65,536 levels per channel; higher bit depth means smoother gradations and more editing headroom.

Heavy colour correction on an 8-bit file can cause visible banding in gradients like skies, while a 16-bit file has enough intermediate tonal values to absorb the same edit smoothly.

An 8-bit RGB image allocates 8 bits, or 256 discrete tonal values, to each of its three colour channels (red, green, and blue). Multiplying those independently addressable values together — 256 × 256 × 256 — yields roughly 16.7 million (16,777,216) possible colour combinations. That ceiling is generous enough for a finished, unedited photo, but it's a comparatively shallow well once aggressive colour correction starts pushing tones toward their limits.

It discards the tonal headroom of the original 16-bit RAW or TIFF, losing what's needed for future heavy retouching or colour grading, since those intermediate values can't be recovered by later re-editing.

Banding appears when a smooth colour transition — a sky, a shadow, a skin tone — needs more distinct tonal steps than the file's bit depth supplies. At 8-bit, each channel has only 256 discrete values, and pushing shadows or highlights hard during colour correction stretches those steps thin, forcing the gradient to jump visibly between bands instead of blending — most noticeable after aggressive edits. A 16-bit file holds far more intermediate values, so the same edit stays smooth.

A DAM's master-retention policy should protect 16-bit files — RAW captures or 16-bit TIFFs — rather than flattened 8-bit derivatives. Sixteen-bit depth preserves far more intermediate tonal values, leaving enough headroom for future colour correction or heavy retouching without introducing banding. An 8-bit derivative has already discarded those intermediate values permanently, so once only the 8-bit version is archived, that tonal flexibility can never be recovered, even by re-editing.