Input lag
Measuring input lag is very different from measuring refresh rate. Input lag is the time taken by the video signal between input to the video port (HDMI/DisplayPort) and display of the image on the screen. Few manufacturers communicate this value, even though it is crucial for gamers. A refresh rate of 1ms is useless if input lag is high. It’s important to note that the more pixels there are to display, the greater the input lag. It will therefore be hard to find very good results on a 4K screen.
Another important piece of information is that not all pixels are displayed at the same time: refresh is from top to bottom. So we’ll find a much better response time at the top of the screen than at the bottom. We take 3 measurements (top, center, bottom) and calculate the average for our rating.
Notation :
- 5 stars – Less than 4ms lag – excellent, e-sport screen
- 4 stars – From 4ms to 8.33 ms – equivalent to one frame lag at 120 Hz refresh rate – good for competitive gamers
- 3 stars – 8.33 to 12.33 ms – more than one frame lag at 120 Hz refresh rate – good for most gamers
- 2 stars – From 12.33 to 16.66 ms – less than two frames at 120 Hz refresh rate – good for most gamers, not recommended for FPSs
- 1 stars – More than 16.66 ms – equivalent to more than 2 frames at 120 Hz refresh rate – noticeable lag in everyday use, not optimal for fast games
The Cooler Master GM27-CQS scores well (5 stars) with 0.5 ms at the top of the screen, 3.6 ms in the middle and 6.7 ms at the bottom. An average of 3.6ms, which explains the 5 stars.
