The AG254FG switches automatically to HDR mode when an HDR10 signal is present. You can still change the picture presets, but no calibration is possible. Brightness is fixed, but you can turn off the variable backlight if you wish.
HDR Brightness and Contrast
The AG254FG easily tops the VESA DisplayHDR 400 standard with over 447 nits peak output. Variable Backlight is turned on by default in HDR mode and you’ll want to leave it on for maximum dynamic range. With the lowest black level here, it hits a best-in-class 11,767:1 contrast ratio. No detail is obscured in either highlight or shadow areas. There is an occasional shifting of the brightness level when content changes quickly, but it is not a distraction during gameplay. Of all the 360 Hz screens I’ve reviewed, this one has the best HDR contrast.
Grayscale, EOTF and Color
The AG254FG’s excellent SDR color accuracy is repeated in HDR mode. The grayscale run shows a bit of coolness at the top, but I could not see that in content. The EOTF tracks perfectly, ensuring full detail rendering at every brightness level from the darkest to the brightest parts of the image. The tone-map transition happens at around 65% which is as expected given the AOC’s peak output.
Most HDR content is mastered with either DCI-P3 or Rec.2020 color. The AG254FG tops out at sRGB but manages to differentiate between Rec.709 (same as sRGB) and DCI-P3 in my tests. This means HDR content will show more saturation in all but the brightest scenery. That encompasses most material, so only the most saturated hues will be missing. This is the best one can hope for when displaying HDR content on an sRGB monitor. Though I wish the gamut were larger, it is as accurate as it can be.