Bit Depth
The number of bits used to represent each colour channel in an image or audio sample. More bits = more possible values = finer gradations. Common values: 8-bit (256 values), 16-bit (65,536 values), 24-bit (audio).
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Bit depth describes how many bits are used to store each sample in a digital file. More bits per sample means more possible values, producing smoother gradations and better quality.
Bit Depth in Images
Each colour channel (Red, Green, Blue) stores brightness values:
- 8-bit per channel: 256 values per channel → 16.7 million possible colours (standard JPEG, PNG)
- 10-bit per channel: 1,024 values per channel → 1 billion possible colours (HDR video, professional photos)
- 12-bit per channel: 4,096 values per channel → 68 billion colours (RAW files, professional cinema)
- 16-bit per channel: 65,536 values per channel → used in scientific imaging and high-end photo editing
Why this matters: With fewer bits, subtle colour gradations in skies, skin tones, and dark shadows appear as visible "steps" — called posterisation or banding. 16-bit editing prevents banding when applying large colour corrections.
Bit Depth in Audio
In audio, bit depth determines the dynamic range (the difference between the loudest and softest sounds):
- 16-bit: CD audio — 96 dB dynamic range (sufficient for consumer music)
- 24-bit: Professional recording — 144 dB dynamic range (captures very quiet sounds clearly)
- 32-bit float: Recording and editing — wide headroom prevents clipping even during processing
Rule of thumb: Record in 24-bit, deliver in 16-bit (CD/streaming standard). The extra bit depth during recording gives headroom for editing without accumulated noise.
Relationship to File Size
Doubling the bit depth approximately doubles the file size for uncompressed formats. 24-bit audio takes 50% more space than 16-bit at the same sample rate.