The Practical Zone System, 4th Edition

 

 

APPENDIX CBit 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 would be 0 and a byte would be 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 4096 levels per pixel and 16 bit images have a bit depth of 65536 levels per pixel.*

Also, in Adobe Photoshop, for technical reasons, 16 bit images only have 32,769 pixel levels instead ...