Can your TV, be used as a monitor? Let's figure it out.

TV broadcasts and video cameras use a clever compression technique called Chroma subsampling that takes advantage of the fact that our eyes are most sensitive to differences in light than color differences. Chroma Subsampling throws out some of the video feed’s color data to allow for more luminance information. So that the picture has enough contrast to appear clear to us while using much less video bandwidth.

How does this work?

Well, when you’re looking at chroma subsampling specifications, you might see numbers like 4:2:2 or 4:2:0. This basically means that if you take a 4x4 block of pixels, only one half or one quarter respectively, of the original color data, will be retained. The luminance data for each pixel is retained fully but applied to only one half or one quarter as many colors.

Chroma subsampling is a widespread standard for movies and TV, which typically use the 4:2:0 method. It’s a big part of the reason you can watch 4K Netflix or YouTube without it constantly buffering. And even non-streaming options, like home Blu-Ray disc players, make frequent use of it. And although this might sound like you’ll end up not seeing accurate colors, our eyes simply can’t tell the difference in many cases. Given that a 4:2:0 subsampled video file only takes up about half as much space as an uncompressed or 4:4:4 file, it is not surprising that it is very commonly used.
But are there times when 4:4:4 is actually important to have? The answer is yes, especially if your screen is connected to a computer. You see subsampling is fine for content with smooth gradations, like movies and sporting events, and even many video games. But if the display you have hooked up to your PC is subsampling, text and other UI elements with sharp edges, can look smudged and blurry.

This typically is not an issue for actual computer monitors, as these are usually designed to display a 4:4:4 signal, but televisions are notorious for undesirable subsampling, which you may have seen for yourself if you’ve ever tried to type a word document or present a PowerPoint presentation or read an article in your browser on your conference room TV via casting or HDMI, an artifact sometimes called fringing. (Pretty hard to read, depending on the background color)

Nowadays though, many modern TVs can be specifically told that they’re connected to a PC, and therefore should not subsample. Typically, if you can locate a setting called something like UHD Colour, Deep Colour, RGB, or something similar, switching to it should force the TV to display your images in 4:4:4. And other times, simply selecting a PC or Computer Mode on your TV will also do the trick.