Input lag (or display lag) is the delay between your GPU sending a frame to your monitor and the monitor actually displaying that frame. This is a very important aspect of gaming, where an input lag of 15ms is preferred.
There is a hidden monitor and TV specification that no manufacturer actually talk about. It’s called input lag and it is one of the most important things to consider when picking a gaming monitor. Input lag, which is also referred to as display lag, is all about the delay a TV, projector or monitor takes to produce an image. Now this includes all the processing of the image, such as scaling/upconverting, frame interpolation and deinterlacing, and this is why TVs often have very bad input lag; over-processing the frames.
Input lag is really only an issue when the subject is gaming. For example, it can be the time you moving your mouse just a little bit and then your character in Overwatch or CS:GO, for example, reacts to that specific action. Input lag is extremely important for FPS games, such as Overwatch, CS:GO, Battlefield and Call of Duty, since every millisecond counts in these games. Now add the already existing delay between your PC or console and the game server in multiplayer games, and you got yourself a very crucial spec for a great gaming experience. This is also why many gamers prefer a 144Hz monitor, since they gain a competitive advantage over 60Hz monitor users. When choosing a gaming monitor, be sure to pick one with less than 15ms input lag.
Keep in mind that input lag and response time are two very different things. Response time is simply the time that a pixel in the panel can change color, often tested as the time it shifts from black to white, or from gray to gray. Response time is the cause for ghosting issues – the longer it is, the longer your monitor will retain an “afterimage”. Input lag is, however, connected with response time, as input lag also includes the response time in the equation. Still wonder: what is input lag? Well, input lag is basically the time it takes for all the image processing to take place added with the response time of the monitor or TV.
Note: We are in the process of making a comprehensive list of monitors sorted by input lag. This requires mass-testing monitors, and we expect it to be ready at the start of 2017. We are sure it will be a great help for those of you looking for an FPS gaming monitor.