Key Takeaways:

  • You can measure input lag using an external device or stopwatch software.
  • Professional lag testing uses an automated input device and oscilloscope.
  • To minimize system latency, use game mode if available, make sure you’re using the native resolution, and set the frame rate to equal the monitor’s refresh rate.
  • You can also use a VGA cable or specialized low latency digital input cables.

Here are some methods for how to test monitor input lag.

When it Matters

Typical input lag, measured in milliseconds, is most often an issue for fast-paced games and competitive eSports play. Minimizing display lag on your top gaming and computer monitor is especially important when playing online multiplayer shooters.

You can measure display lag using a dedicated test device such as the Video Signal Input Lag Tester, or you can employ a DIY solution. A number of technical outlets such as Blur Busters employ photodiode or light-sensitive resistor-based input lag testers. If you’re slightly handy with electronics, you can make such a device with minimal investment.

Display Lag Versus Response Time

Monitor and Smart TV manufacturers usually include pixel response time in their specifications, but they rarely list a figure for total input lag. Signal processing and image resizing can introduce additional input lag on many LCD screen devices.

Pixel Response and Input Lag Tests

To test for display lag, you’ll need to test the total latency of the system. You can do this a few ways, but essentially the principle of these lag testing methods is the same: a high-speed camera connected to your input device, recording the total time between initiating a signal and the image appearing on the display screen. Input lag measurements, in milliseconds, can be derived from the total latency minus the specified response time.

Hardware Tests

This method involves using an external device with a light sensor that sends a simple video signal to your display screen via HDMI cable and then records the time between sending the signal and the light sensor registering the output. These devices can only measure the display lag intrinsic to the monitor, however. This makes them useful for comparisons between different gaming monitors, but less useful for finding out the total real-world latency of a system.

Software for Lag Testing

Some lag testing methods use software called SMTT. Assuming your graphics card driver is compatible, this software streamlines the process of obtaining input lag measurements. When installing lag testing software, make sure the program is compatible with your graphics card driver.

Tip: When installing lag testing software, make sure the program is compatible with your graphics card driver

Response and Input Lag Tests for High Refresh Displays

If your monitor has a refresh rate of over 60Hz, you’ll need to make sure you’re using a recording device that also functions at 60Hz or higher. This means, if you’re using a camera you’ll need to film at 60fps or faster to keep your lag tester accurate for these types of displays.

Middle Screen Readings and Screen Uniformity

While many input lag testing methods measure middle screen response, there can be an input lag difference when looking at different parts of the screen, due to the way the refresh cycle operates. To control for this, some lag measurement methods sample multiple points on the screen. Since LCD monitors refresh the image from top to bottom, the first-on-screen reaction may be ahead or behind middle screen readings by as much as 1/2 frame. Depending on the frame rate this can be anywhere from less than a millisecond to over 15 ms.

Warning: Since LCD monitors refresh the image from top to bottom, the first-on-screen reaction may be ahead or behind middle screen readings by as much as 1/2 frame

Picture Settings

When performing an input lag test, make sure to check picture settings and turn off any image processing features that affect input latency. These features include G-SYNC or Vsync or game mode as used in various gaming monitors. Running at a non-native resolution can also affect display input latency and introduce additional errors.

Warning: Running at a non-native resolution can also affect display input latency and introduce additional errors

Causes of Display Lag

Signal processing technology and buffering to the monitor’s refresh rate are some common sources of additional latency on monitors Smart TVs. On some OLED and LCD screen devices, different colors may have different lag measurements as well, due to the properties of the individual pixels. Different connection methods also introduce variables. Analog VGA cables typically have the lowest additional lag.

Warning: Analog VGA cables typically have the lowest additional lag

STAT:

The average lag time of an LCD monitor is around 17 to 40 ms, depending on the testing methodology.

The best gaming monitors can get the lag time down to the sub 10 ms level.

Sources:

http://hdtvlag.googlepages.com/ourtest

http://www.prad.de/new/monitore/specials/inputlag/inputlag-teil18.html

TFT Central – Display lag and TFT features

Database with measurements from input lag for over 200 televisions (German)

https://en.wikipedia.org/wiki/Input_lag

Input Lag Testing Method For Monitors FAQ

How is input lag measured?

Typically, whole-system input lag is measured using high-speed photography and an automated input signal.

How can input lag be less than 10 ms on a 60 Hz monitor?

Input lag can be measured using different points on the screen. While a 60 Hz monitor may theoretically take 1/60 second to render a complete frame, parts of the display may change faster than others. Technologies such as Vsync can cause this apparent reduction in lag.

What is monitor input lag?

Monitor input lag, distinct from "response time" generally refers to the total delay between initiating a signal and the image changing on the display.

How do I reduce input lag?

Some gaming monitors have features designed to minimize input lag, by turning off added image processing functions; this may result in slightly more artifacts or less "smooth" picture quality while reducing latency. If your monitor has an analog input, you can also try connecting using a VGA cable rather than an HDMI or USB.

Ryan Mcbride

Ryan McBride is a writer based in Los Angeles. He has contributed work to magazines and sites including Gayot, Spy, Paper, Ladygunn, 3AM and the Crab Creek Review. He writes consumer reviews, essays, science and tech journalism as well as literary and art criticism.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *