The XG27AQ supports HDR10 signals and switches formats automatically. Both G-Sync and FreeSync are available in HDR mode at 170 Hz over DisplayPort. Two picture modes are available, Gaming and Cinema.
HDR Brightness & Contrast
The XG27AQ is very bright with over 455 nits of peak HDR output. Both Gaming and Cinema HDR modes produce the same brightness and contrast results. The variable dimming option is turned on and delivers spectacularly low measured black levels and an impressive contrast ratio of 22,506.9:1. It doesn’t get much better than that. Though the XG is not a full-array zone dimming panel, it creates very good HDR, especially when the content is bright.
Grayscale, EOTF & Color
HDR grayscale and color performance is nearly identical for both Cinema and Gaming modes so we’re showing the charts from our tests in Cinema. Grayscale is neutral until the mid-range where it becomes a little cool in tone. The error is relatively low and hard to spot in actual content.
The EOTF runs too dark up to the tone-map transition point. There, the XG27AQ is a little late with an actual transition at 75% rather than 65%. The luminance errors appear to be due to the dynamic contrast’s slow changes to picture content. Static images look quite good but sometimes, the shifts in luminance lag behind changes in image brightness. How pronounced the effect is will depend on what you’re watching or playing, and it won’t always be visible.
HDR color is fairly accurate with some oversaturation in the mid-tones. This gives HDR images more punch while retaining good detail and depth. The XG27AQ performs much like its competition in this test.