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Grayscale and Gamma Tracking
Our grayscale and gamma tests use Calman calibration software from Portrait Displays. We describe our grayscale and gamma tests in detail here.
The X27U starts in its Standard picture mode, and it is right on the edge of needing calibration. I would say it does and others might say it doesn’t. The warmth indicated in the first chart manifests in brightness steps above 60%, so if you’re looking for it, you’ll see it. And if you’ve read this, you might be unable to unsee it. Gamma is a tad dark, closer to 2.3 or perhaps the BT.1886 standard. But my color tests indicate the X27U is a power gamma monitor.
Calibration removes all visible grayscale errors. I only had to adjust the gain sliders; the bias controls are unchanged. Gamma is a tiny bit lighter, but visually, there is no difference. When contrast is this high, dark gamma is forgivable. And if you want it lighter, that option is available in the Color menu.
Comparisons
A premium monitor like the X27U should be on-point out of the box, and it nearly is. It’s possible that other samples would measure better than mine, but I’m being very picky here. 3.06dE is nothing to complain about. Thanks to the precise controls, reducing the error to 0.94dE is something to be happy about.
Gamma tracking is tight with just a 0.17 range of values, which is about average for the group. The deviation of 4.09% equates to an actual value of 2.31. It's a bit out of spec but forgivably so. I’d rather the gamma be too dark than too light.
The sRGB mode is fixed with no option for calibration. Grayscale tracks a bit warm, and gamma is relatively close to the 2.2 reference with slightly dark values at 60% and above. This is acceptable for a gaming monitor but with a few more adjustment options, it could be a pro screen.
Color Gamut Accuracy
Our color gamut and volume testing use Portrait Displays’ Calman software. For details on our color gamut testing and volume calculations, click here.
The X27U has a huge color gamut with near-100% coverage of DCI-P3 and it hits every target with a 1.73dE average error. This is superlative performance. Calibration takes the error down to just 0.95dE which is a really good thing. There are few monitors that can get under 1dE in my gamut test.
The sRGB gamut is also very accurate, with no visible errors and an average of 1.98dE. The lack of calibration options hasn’t affected gamut accuracy, but it would be nice if one could dial in the grayscale tracking. This is a minor flaw.
Comparisons
The X27U’s color gamut score of 0.95dE is one of the lowest I’ve ever recorded. Many pro monitors can’t achieve this. This is in reference to DCI-P3. The sRGB score is very good at 1.98dE so it can be used for color-critical applications if you can forgive the slightly warm grayscale tracking. As you can see, there isn’t a bad OLED in the bunch. They all have excellent color accuracy.
They also all have excellent color volume. For LCDs, the average is around 92% but clearly, OLEDs are a more colorful technology. And a Quantum Dot layer is not a prerequisite. The Philips and Samsung screens have them, so their gamuts are a bit larger. But 99.51% coverage is nothing to complain about. The X27U is extremely colorful and hits full saturation for every color. It also covers all of sRGB with a tiny bit of bonus red.
Test Takeaway: Between the X27U’s wide and accurate color gamut, and its high contrast, there are few, if any, monitors that are more colorful. It isn’t quite as accurate as others before calibration but once adjusted, it rises to the top. The picture is stunning in every respect.
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