Our grayscale and gamma tests are described in detail here.
While the XB280HK isn’t premium-priced relative to competing Ultra HD screens, it is an expensive gaming monitor. For your money, you’re getting decent grayscale performance out of the box. In the Standard picture mode, you really don’t have to make any adjustments to enjoy accurate performance. At 100 percent, the white point starts to go a little blue. But upping the Contrast control one click will fix that.
An instrumented calibration brings the errors down to almost nothing with just a few tweaks. The result is fantastic.
Here is our comparison group:
The XB280HK takes top honors for out-of-box grayscale performance. We expect that a majority of gamers will not calibrate their monitors, so if accuracy is important to you, there are few better choices in the G-Sync or FreeSync segment.
The AOC takes first place by the slimmest of margins. A difference of .04dE is essentially a wash.