Chroma Subsampling Explained: 4:4:4 vs 4:2:0

Chroma subsampling is a technique that reduces color information while preserving brightness. It is invisible in most photographs but saves significant file size.

Color and Brightness

Images have two components: luminance (brightness, what we see) and chrominance (color). Human eyes are 4x more sensitive to luminance than chrominance.

4:4:4 (Full Color)

Every pixel has full color information. Largest file size, highest quality. Used only in high-quality workflows and lossless formats (PNG).

4:2:2 (Half Chroma Horizontally)

Color information is halved horizontally. Every other pixel shares chroma with its neighbor. Smaller file size, imperceptible quality loss.

4:2:0 (Quarter Chroma)

Color information is halved both horizontally and vertically. 75% of color pixels are interpolated. Saves 50% file size vs. 4:4:4. Invisible to human eyes.

JPEG Default

JPEG typically uses 4:2:0 subsampling by default. You can force 4:4:4, but the file is ~25% larger with no visible quality improvement.

When It Matters

Photographs: 4:2:0 is perfect. Screenshots and graphics with sharp color edges: 4:4:4 may prevent slight color fringing.

Video Codecs

H.264, HEVC, VP9: all use 4:2:0 by default. Keeping color information full (4:4:4) requires extra bandwidth or storage.

Practical Recommendation

For photographs, use 4:2:0 (JPEG default). For graphics or when quality is paramount, use PNG (4:4:4 implied, lossless).