Problems · How to check
Why is text blurry on my TV when I use it as a monitor?
Because the TV is receiving colour at a lower resolution than brightness. Video is sent that way on purpose, since eyes barely notice it in pictures, and TVs expect video. Text and thin coloured lines notice it at once: edges smear and pick up fringes, especially red or blue on a contrasting ground.
The chroma subsampling test shows one-pixel red lines and red text on blue. If they are smeared, the TV is subsampling. Naming the HDMI input PC, or turning on the input's deep colour or enhanced format setting, makes the TV accept full colour, and text sharpens immediately.
First, notice when it happens
The causes, ranked
1. Chroma subsampling on the HDMI input
most commonHow to confirm it
Red text on blue is fringed in the chroma test; black text on white looks nearly fine. TVs default to 4:2:0 or 4:2:2 on inputs not marked as PC.
The fix
In the TV's input settings, rename the HDMI input to PC, or turn on the setting called Deep Colour, Enhanced format, Input Signal Plus or UHD Colour for that input. Then run the test again.
2. The PC is not at the TV's native resolution
commonHow to confirm it
The resolution in the system's display settings is not the panel's, or scaling is set to a value that lands text between pixels. Everything, not only colour, is soft.
The fix
Set the native resolution (3840 by 2160 on a 4K TV) and a scaling factor of 100, 150 or 200 percent, which keep pixels whole.
3. The cable or port cannot carry full colour at this rate
commonHow to confirm it
The graphics driver will not offer RGB or 4:4:4 at 4K and 60 Hz, or offers it only at 30 Hz. HDMI 2.0 carries 4K 60 Hz at full colour only just; older cables do not.
The fix
A certified high-speed HDMI cable and an HDMI 2.0 or 2.1 port on both ends. Failing that, 4K at 30 Hz with full colour is sharper for desktop work than 60 Hz subsampled.
4. A picture mode meant for film
occasionalHow to confirm it
Text looks oversharpened or haloed rather than smeared; the TV is in a Vivid, Dynamic or Cinema mode with sharpening and noise reduction on.
The fix
Use the Game or PC picture mode, or a standard mode with sharpening at zero and noise reduction off.
Measure it instead of guessing
The chroma subsampling test draws one panel pixel wide, whatever the screen's scaling, and asks whether the red lines and text are sharp or smeared. The answer names the TV setting to change.
What software cannot tell you here
- A page cannot read the colour format the cable is carrying; it can show a pattern that makes the difference plain to your eyes.
- It cannot change the TV's settings; the menu names differ by maker and the article lists the common ones.
Asked, in people’s own words
- What is 4:4:4 chroma?
- Colour sampled for every pixel, the same as brightness. 4:2:2 and 4:2:0 sample colour for every second pixel or every second row and pixel, which is fine for video and smears text.
- Why does renaming the HDMI input to PC fix it?
- Because most TVs treat an input named PC as a computer and accept full colour on it. It is a label the TV uses to choose the signal mode, not just a name.
- Is a TV as a monitor a bad idea?
- Not for most uses once colour is full and the picture mode is Game or PC. Input lag, pixel density at desk distance and text clarity are the things to check, and the lab's tests cover the last.