Results: Pixel Response And Input Lag
To perform these tests, we use a high-speed camera that shoots at 1000 frames per second. Analyzing the video frame-by-frame allows us to observe the exact time it takes to go from a zero-percent signal to a 100% white field.
The pattern generator is placed at the base of the monitor so our camera can capture the precise moment its front-panel LED lights up, indicating that a video signal is being received by the monitor. With this camera placement, we can easily see how long it takes to fully display a pattern after pressing the button on the generator’s remote. This testing methodology allows for accurate and repeatable results when comparing panels.
Here’s a shot of our test setup. Click on the photo to enlarge.
The brighter section of the camera’s screen is what actually appears in the video. You can see the lights of the pattern generator in the bottom of the viewfinder. We flash the pattern on and off five times and average the results.
Here’s the screen draw result.
The screen draw time matches most of the IPS monitors we’ve tested. But a 4K monitor probably won't be the choke point for performance when you're driving this many pixels. Even with the fastest video cards, you won't be pushing more than 60 FPS in most games.
Although the IGZO technology Asus is using offers theoretically faster response times, there are obviously other factors in the signal chain preventing measurable gains. At least for now, it’s safe to say that 4K monitors aren't the fastest option for fast-paced gaming.
And here are the lag results.
This is pretty much expected performance for a 60 Hz IPS screen. And since Asus' PQ321Q is the first IGZO-based display in our chart, it gives us a baseline for that technology, too. We don't anticipate these input lag measurements being an issue until modern graphics subsystems become more powerful. And the display's processing power matters as well. The control circuitry needs to catch up before the technology's advantages are fully realized.