What is Chroma Subsampling?
Chroma subsampling stores color-difference information at a lower spatial resolution than luma information. Formats such as 4:2:0 and 4:2:2 trade color detail for lower data rates.
How Chroma Subsampling works
Digital component video can place luma samples on a finer grid than its color-difference planes because human vision is generally more sensitive to brightness structure. The familiar ratio notation summarizes horizontal and vertical chroma sampling over a luma region, but it does not fully describe sample siting, interlaced handling, bit depth, or matrix. Subsampling is selected during capture and encoding and may be converted again at editing, compositing, or display boundaries.
Key facts
- In 4:4:4, every luma position retains corresponding chroma resolution; 4:2:2 halves horizontal chroma resolution, while 4:2:0 also reduces it vertically.
- Two 4:2:0 streams can use different chroma sample locations relative to luma. Ignoring that siting during conversion can shift colored edges even when dimensions and bit depth match.
- Repeated downsampling and upsampling can soften saturated boundaries and colored text. Keeping a higher-chroma intermediate avoids compounding that loss before final delivery encoding.
When Chroma Subsampling matters
Select 4:2:0 for efficient delivery when broad playback compatibility matters, and retain 4:2:2 when editing or keying needs more color detail. Heavy subsampling can blur colored text and sharp color boundaries.