Input lag vs response time

Susan Fernandez November 11 2021

Before you buy a new gaming monitor, you will be overwhelmed with key figures such as input lag and response time. Here we will explain what these mean and which ones are the most important.

What are response time and input lag?

Response time

The response time describes how quickly a pixel can change its color. Pixels must be able to change their color very quickly, especially for fast movements on the screen - otherwise, the image appears spongy, in extreme cases, there even seems to be "ghost images" or graphic streaks behind it. 

For example, if a car moves on the screen, its color changes and ideally remains changed all the time - including in the still transition period when it comes to rest.

You should watch the values in the manufacturer's specifications for the response time: values ​​for the absolute optimal case are often given here, which, however, almost never occur in practice.  As a rule, one does not find any kind of "average value".

But we can reassure you: the response time was still a major problem a few years ago, so precise measurements, for example from complex tests, were important. 

Nowadays, however, all modern monitors are basically fast enough in terms of their response time to guarantee unadulterated gaming fun - at least if you take a model with the widely used TN panel.

With a manufacturer specification of up to about 6ms (milliseconds), you are definitely not doing anything wrong. The response time should not be confused with the input lag. 

Input lag

The input lag describes how long it takes for you to change something with your mouse or keyboard until it has been processed by the computer. It describes whether there is an additional delay between the point in time at which the image from the graphics card arrives at the monitor and the point in time at which the image appears on the monitor, regardless of the response time of the pixels. 

Such a delay often occurs with LCDs -TVs, if "picture improvement" features are active there. In extreme cases, such a lag can be noticed by moving the mouse, for example, and the mouse pointer on the screen only reacts much later. In the case of PC monitors, however, input lags generally do not play a role.

If you play fast-paced games, then it is obviously better if less time passes between your input and execution of that command. For example, in Counter-Strike, every millisecond counts when you try to hit an opponent at higher speeds. At low speeds, there are no problems - but as soon as higher speeds come into play, the input lag is critical.

As a rule, inputs with high IPS (input per second) ratings have less input time than those that are low on this scale.

However, there are other factors that also affect the delay: if you move your mouse across its entire area quickly and then push it down very slowly at a specific point, you may notice a significant difference in latency between the two movements - even though they both involve exactly the same number of signals from your mouse. 

What do manufacturers mean?

Both response times and input time are usually measured by computer monitors via self-developed tests. In these tests, well-established patterns or things like boxes or letters are displayed on the screen and then disappear again.

Sometimes there are also white, dark, or even colored screens that are flashed for a fraction of a millisecond. For these self-developed measurements, companies use additional tools in the form of hardware and software to assess the results more accurately.

However, it must be said that since manufacturers carry out their own tests, they can basically provide whatever values ​​they want. In addition, a test is not necessarily displayed at all refresh rates, which can lead to misleadingly high results because there were no problems when simply displaying static images.

In practice, input lags usually occur if you display any kind of dynamic image - although in extreme cases this behavior occurs even when displaying plain color fields with high IPS ratings.

Why response time is more important?

Gaming monitors are often advertised as having a fast response time and there is a reason for that. It is probably the most important metric when it comes to professional gaming. The response time indicates how great the input lag of a monitor is. With a response time of 3 milliseconds, for example, it takes 3 milliseconds for input from the mouse or keyboard to arrive on the screen.

A quick response time is accordingly better and ensures that the input lag is as low as possible. This in turn ensures that the game controls itself crisply, which is a great advantage, especially in competitive online games or games that require fast reaction times.

If you are not a gamer - does it matter?

Many people will be fine with a normal monitor and do not need to worry about input lag and response time.

Even for gamers, there is no point in prioritizing this factor above all else: Provided that the IPS rating remains within reasonable limits (ideally 5 – 20 ms ), it should not really matter whether your monitor's response time is 1 millisecond slower than another model. After all, such deviations can also be caused by other factors such as graphics cards.

But if you don`t use your computer for gaming, there is no point to buy an expensive gaming monitor which does not fit your needs.

There are also some other variables that may be important for you: the form factor, the design, or even compatibility with multiple devices. This can easily lead to different price ranges and decision criteria.   

What should you look out for?

Input lags of monitors change depending on what is being displayed. If you want to test this yourself, simply open a game that is relevant to you and then stop moving your mouse completely before opening another program, such as Windows Explorer or Task Manager, which will display all running processes in thumbnail preview mode (switch off "Show window contents while dragging" in the options if it doesn't work).

Input latencies can be clearly and quickly identified by the delay time that occurs when you click on an open window.

In addition, games themselves often have a benchmark function that can display the response times/input lags in milliseconds. In many cases, these values ​​are also displayed during loading. This information is very helpful if it is important for you to determine whether a certain monitor has sufficient performance or not.

Considerations when buying a monitor

There are a few things to consider when buying a gaming monitor. The most important features here are the response time and the frequency (Hertz number) if you want to have a smooth gaming experience. If you can compromise on resolution, i.e. you don't necessarily need 4K, you should be able to find good gaming monitors at fair prices without any problems.

The best-known brands in the monitor market are well suited for gaming purposes and offer models with fast response times and relatively low input lag, which is very important.

If you like to play online games and make use of a high monitor resolution (such as 2K or 4K), you should pay attention to the refresh rate that your desired monitor has. This is usually advertised as Hertz. A higher rate allows for smoother gameplay - even though normal full HD monitors can handle most current games without problems.

The 144-hertz range can currently be considered state of the art when it comes to refreshing rates. They guarantee an extremely fluid experience, even in far more demanding games such as Assassins Creed Origins or Battlefield 1.

Input lag and TVs

TVs are not quite as critical for input lag as monitors, simply because the opportunities to play fast-paced games on TV are very limited. Picture processing can also cause problems that are not seen during desktop use or when watching movies.

If you sometimes enjoy fast-paced shooters with your friends, it is worth looking for TVs that have a low latency time. This will be recorded in milliseconds and does not represent the total latency times, which may be considerably higher depending on your other equipment.

Currently, TVs with an average of 15 ms are considered good - although many models from certain manufacturers offer significantly faster models (e.g., LG OLED ). But even this value ​​can easily double when you watch HDR content (which requires more processing power).

If you want to play online games on your TV, it is also important that the sound system has an optical output for connecting headphones. This may seem like an unnecessary expense, but can help reduce input lag significantly (e.g., the Samsung JU7100, low input lag: 15ms; headphone jack: 9 ms).

A word of warning

Response times and input latencies are not listed for monitors by all manufacturers. This information can often be found in reviews or other reputable sources if you don't want to take the manufacturer`s claim at face value.

If nobody knows anything about it, how should you decide whether this information is actually true? Either way, it's always worth asking at stores - just be aware that you may not get an honest answer.

When it comes to gaming, there are also other factors that can affect response times and input lag. GPU, CPU, memory frequency, drivers, Windows Settings (especially with multiple displays), display driver settings, or even the connection between your mouse/keyboard and the PC is only a few of these factors that are often ignored.

We will not go into detail here - but if possible, it is always worth testing different monitors in person to see if they really provide what their specs suggest.

Aeronautics engineers have known for years how valuable milliseconds can be when lives are on the line. It's about decision-making - so let`s dig into this matter.

Final word

If you play online, choose a monitor with a good refresh rate and low input lag if possible. You will notice the difference in responsiveness immediately.