Results: Pixel Response, Input Lag and Blur Reduction
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.
Since our pattern generator tops out at 60 Hz, we connected the PG278Q to a PC for the speed tests. We use the same high-speed camera (1000 frames-per-second) to film a mouse movement that tells us the total input lag and screen draw time. We film five iterations and average the results. G-Sync and ULMB are turned off, and the refresh rate is locked at 144 Hz.
The top four monitors all run at 144 Hz, while the Overlord hits 120. The correlation between screen draw and refresh rate seems pretty consistent. The 120 Hz IPS screen is just a little slower. A five- or six-millisecond result is about as fast as it gets for now. The only remaining question is: can a 144 Hz IPS screen match its TN competitors? We’ll have to wait and see.
Here are the lag results:
As expected, input lag is extremely low. Remember, this is straight-up 144 Hz with no v-sync or G-Sync. Of course, you don't suffer any lag penalty with G-Sync, but you do with v-sync turned on. Ultimately, signal rate-matching and low input lag are the best combination, which is precisely what G-Sync offers.
Motion Blur Reduction With ULMB
To use ULMB (Ultra Low Motion Blur), you need an Nvidia graphics board with its refresh rate set at 85, 100, or 120 Hz and G-Sync turned off. You can’t use both features at once.
With any kind of backlight strobing, there is a tradeoff in brightness. Luckily, the PG278Q has plenty to spare, so if you want to use ULMB, we suggest turning the backlight up to its maximum settings. That's exactly what we did for our tests.
Brightness with ULMB on is also affected by refresh rate. The lower the rate, the higher the output. Asus thoughtfully includes an OSD adjustment for the pulse width. It’s like the utility we used in the BenQ XL2720Z review. Changing the pulse alters brightness from a maximum of 100 down to a minimum of 10. The charts below show both extremes at all three ULMB-supported refresh rates.
The smallest reduction in output hits at 85 Hz, where you give up 57-percent brightness. Even this least-aggressive setting improves motion resolution significantly. We observed several moving detail tests from BlurBusters and saw obvious benefits.
Black levels change at the same rate as white levels, so you won’t really see much change in contrast. The choice comes down to your preferred light level.
Of course, the greatest measured contrast comes at a uselessly-low output level. Our favorite setting is 85 Hz with Pulse Width on 100. A ratio of 874 to 1 is still very respectable.
Choosing between G-Sync and ULMB comes down to the kind of game you’re playing. For fast motion with wide-varying frame rates, G-Sync will eliminate frame tears and stuttering. In a more fluid title where the frame rate doesn’t change as much, ULMB creates a better look. In either case, input lag and response time stay low thanks to the Swift’s speedy 1 ms panel.
