The Practical Zone System for Film and Digital Photography, 5th Edition

Appendix D   

Bit Depth

Computers store information electronically in the form of a number that at the simplest level can either be 0 or 1. This is called one “bit.” An 8-bit number in a computer has 8 digits and is called a “byte.” So, an example of a bit is 0 and a byte is 0000 0000.

Here is how bit depth is notated in digital photography:

8-bit images have a bit depth of 256 levels because if you multiply the number 2 by itself 8 times the result is 256 (2 — 4 — 8 — 16 — 32 — 64 — 128 — 256).

By this same logic, 12-bit images have a bit depth of 4,096 levels per pixel, and 16-bit images have a bit depth of 65,536 levels per pixel.^* Also, in ...