Display Lag
How does a display introduces lag?


This section will be shorter than the others because this topic has been addressed by others. Here are some links that go deeply in this:

The gist of it

As we have seen in the game engine section, a video signal consist of sending pixels one at a time, from top-left to bottom-right. It is the duty of the display to present those pixels to the user.

A screen can be abstracted like this: it gets a pixel, this pixel is translated to electrical characteristics for the target display technology (example red: 1.2V, blue: 0.5V, green: 0.2V), then it transmit this data to the physical pixel that may also take time to reach a stable state.

Display Lag Chain

If we look at some example technologies:

Variable Refresh Rate

The Variable Refresh Rate technologies (G-Sync or FreeSync) are an alternative that is able to transmit the frame faster allowing the controller to be able to send the video at a irregular pace. The main advantage is that the display is better synced to the game engine allowing better latencies.

For in-detail results, consult the guides by blurbusters.

Smart TVs

The Smart TVs have been notorious to introduce major lag issues. The main concern is that the display lag chain is a bit different. Smart TVs will use somewhat of a capture device that will read the frame buffer over HDMI. Then they may apply filters and compose the frame within the smart TV operating system and its UI. Depending on how well the TV is built, this costly process may introduce several frames of lag.

That is why most TVs nowadays support a "gaming mode" that by-passes most of this processing to get a faster result.


To measure display input lag you must have a video signal that you trust to be extremely stable. Afterwards, you need to have either a high speed camera, or a specific device.

Specific devices

There are three devices to my knowledge that are able to compute input lag.

The main advantage is that you will get a fixed value showing you precisely what is the display lag. They are great to showcase screen that have a major lag problems (+1 or 2 frames).

Several caveats:

High speed camera

Blurbusters made a great article on how to properly measure using a high speed camera. This will cover all the previous issues that you can find using specific devices but it requires expensive hardware and more time to analyse the results.