Real World Digital Photography, 2nd edition

Bit Depth

Bit depth describes the number of bits used to store a value, with the number of possible values growing exponentially with the number of bits (Table 2.2). A single bit can store up to two possible values (black or white) while 2 bits can store up to four possible values (black, white, and two shades of gray), and so on (Figure 2.6). Digital image files are stored using either 8 or 16 bits for each of the three color channels that define pixel values (see “Color Modes” later in this chapter).

Table 2.2. Bit Depth

Bits	Tonal Values Possible
2	4
4	16
6	64
8	256
10	1024
12	4096
14	16,384
16	65,536

Figure 2.6. As the bit depth increases, the number of possible tonal values grows exponentially.

8 Bit vs. 16 Bit

The difference between an 8-bit and a 16-bit ...