Bit-depth
Bit depth is an enormously important facet of computer systems. In simple terms, bit-depth expresses the number of bits in a byte. For example ... a byte made up of 8 bits (eg "10011101") has a bit-depth of 8. We can also say this byte is 8-bit. Bit depth is also known as word length.
Possible values of a byte
Bit-depth determines the number of possible variations a byte can be. For example, there are 16 possible variations in a 4-bit byte ...
| Byte (binary) | Equivalent decimal value |
|---|---|
| 0000 | 0 |
| 0001 | 1 |
| 0010 | 2 |
| 0011 | 3 |
| 0100 | 4 |
| 0101 | 5 |
| 0110 | 6 |
| 0111 | 7 |
| 1000 | 8 |
| 1001 | 9 |
| 1010 | 10 |
| 1011 | 11 |
| 1100 | 12 |
| 1101 | 13 |
| 1110 | 14 |
| 1111 | 15 |
See computer counting systems for more on base 2 (binary) and base 10 (decimal) counting systems
Here are some other typical bit-depth values ...
| Bit depth | Byte length | Example Byte | Possible values | No of values |
|---|---|---|---|---|
| 1 | 1 bit | 1 | 1 and 0 | 2 |
| 8 | 8 bits | 10010011 | 00000000 to 11111111 | 256 |
| 16 | 16 bits | 1001001110010011 | 00000000 - 00000000 to 11111111-11111111 | 65,536 |
| 24 | 24 bits | 100100111001-001100111010 | 00000000 - 00000000 - 00000000 to 11111111- 11111111-11111111 | Millions! |
Bit-depth and quality
As a general rule ...
- The higher the bit-depth the better the quality, but ... the bigger the file size, and the greater the processing power required to handle it.
- The lower the bit-depth the poorer the quality, but ... the smaller the file size, and the lesser the processing power required to handle it.
Differing bit-depths
As a general rule, the bytes in an individual software element (eg an image file, application or system component) will have identical bit-depths. There are some exceptions such as the MP3 format which offers a variable bit-depth option, but this is not the norm.
However, bit-depth may differ between software elements in a single computer system. For example, a system may be dealing with all the following file types simultaneously ...
- A GIF image file which will comprise a number of 8-bit (or less) bytes
- A CD quality .aif or .wav audio file which will comprise a number of 16-bit bytes
- A native RGB Photoshop document which will comprise a number of 24-bit bytes
- Elements of an operating system some of which may be 32-bit whilst others are 64-bit
It is possible for a single application to handle different media files of different bit depths simultaneously. For example ... Flash can replay audio, display images and play video files each with a different bit-depth.
Bit depth and audio
Click here to read how bit-depth effects quality in an audio file.
Bit depth and images
Click here to read how bit-depth effects quality in an image file.
Related downloads
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