West Penn Wire Blog

What is Chroma Subsampling?

Posted by Samantha Bante on Oct 23, 2017 9:00:00 AM

In previous blog posts we have discussed 4K resolutions, what it does for images on a screen, as well HDMI Cables. But, one important component to understand is what defines the details of the image, Chroma Subsampling. Chroma Subsampling can definitely be a difficult topic to understand, but this post will explain what it is and how it could affect the images on your screen. 

What is Chroma Subsampling?

Chroma Subsampling helps to reduce the color information in a signal to provide the clearest image and is also known as the color resolution. An electronic image is made up of pixels and composed of a few different characteristics- let's work through these a bit..

Each pixel is composed of two major elements:

1) Luminance: which defines the pixels brightness

2) Chrominance: which defines what color a pixel is.

Note: Each pixel needs to have its own luminance, but doesn't need to have its own chrominance because color can be shared among pixels, while brightness cannot

Now, let's break it down the differences between 4:4:4; 4:2:2 and 4:2:0:

The number of pixels that share color is determined by what type of chroma subsampling it is. Each sample is defined by a block of 8 pixels. The first number refers to the size of the sample and its pattern, which is typically 4 pixels wide. The second number refers to how many pixels in the top row will receive color or chroma sampling. The third number shows how many pixels on the bottom row will receive chroma samples

Each pixel sample is comprised of 8 pixels- 4 on the top row and 4 on the bottom row.

4:4:4

Each of the four pixels in the upper row gets its one luminance (brightness) and chrominance (color) information as well as each lower row gets its own brightness and colors too. This is typically used for very high-end professional video- or rather not something a typical consumer should be concerned with.

4-4-4.jpg

4:2:2

In this sample, every two pixels on the top have to share color sampling and every two on the bottom have to share the same color sample. Meaning that roughly 50% of the color is lost. This is more commonly used by professionals within today's market and video production. 

4-2-2.jpg
4:2:0

This color sample shares chroma, BUT the bottom row receives no color samples of its own. They are then required to share with the row above. Meaning that much of the detail within the images are lost. Subsampling for most technology now is defaulted to 4:2:0 such as Blu-Ray. 

4-2-0.jpg

 

Want to learn more about 4K and resolutions and which HDMI cables can fit your needs? Click below to learn more:

Learn more about 4K/HDMI Cables

 

Topics: 4K Resolution, 4K, 4:4:4, 4:2:2, 4:2:0, Chroma Subsampling