To read about our monitor tests in-depth, please check out Display Testing Explained: How We Test PC Monitors. We cover brightness and contrast testing on page two.
Uncalibrated – Maximum Backlight Level
Mini LED excels in brightness with VESA DisplayHDR 1400 ratings across the board. That means the XG321UG is also very bright in SDR mode, hitting over 600 nits peak. This is a lot of light, especially for such a large panel. Turning the brightness up all the way will amply illuminate a medium-sized room with no other light source present. With a minimum brightness level of 39 nits, the 100-step brightness control becomes rather coarse. Each click changes the level three to six nits making precise levels harder to achieve.
The XG321UG’s black level is very high at maximum brightness, but contrast is quite good at 1,210.3:1. This is higher than average for IPS panels in general and just below the number I recorded for the Asus PG32UQX, the only other Mini LED screen in the group.
After Calibration to 200 nits
When the monitors are equalized with calibration and a 200-nit output setting, the XG321UG sits solidly in third place with 1,102.8:1 contrast, a bit lower than the Asus PG32UQX and Philips 329M1RV but comfortably above the bottom three. This is a difference one can see in a side-by-side comparison. Native contrast is excellent here and when you turn Variable Backlight on for SDR content, it becomes even better.
ANSI contrast is also a solid third-place result for the XG321UG. The Philips is exceptional in this test, but the two Mini LED screens are close behind. The top three monitors are all made with very high-quality panels that feature precisely fitted grid polarizers and good quality control.