The GP27U defaults to its User 1 mode, so I used that preset for all measurements and calibrations. Though the signals here are SDR, it uses its full gamut, which is much larger than sRGB. I consider the GP27U a Rec.2020 monitor, and I’ll explain why below.
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 GP27U’s grayscale tracking is a bit cool by default. I recommend calibration though some users will be satisfied with errors this small. Gamma is a tad light, but this is also a small error.
Calibration results in professional-level grayscale tracking, but gamma is still a little light. It isn’t a big problem, but it could be better, given the excellent results I observed in every other metric. The results above were recorded without local dimming engaged. Turning it on Low enhances contrast and depth significantly.
If you choose sRGB or any other gamut preset from the Color Space menu, the grayscale is cool and cannot be adjusted. Gamma is light here as well. While these additional modes deliver decent gamut accuracy, their grayscale and gamma tracking have room for improvement.
Comparisons
The GP27U’s 4.55dE default grayscale score isn’t bad but compared to the competition, it could be better. Since the error is concentrated in cooler tones, it isn’t too obvious. Calibration puts Cooler Master on top though so it’s well worth making the adjustments.
The gamma comparison is similar. Though the GP27U is in last place, its gamma errors are minor. It’s just that the other monitors are more precise. Once local dimming is engaged, it’s a moot point because the picture will have much deeper blacks and brighter highlights.
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.
Nearly all wide gamut monitors follow the DCI-P3 standard. But a few try to cover Rec.2020, and that’s what the GP27U is doing. You can identify this by the green hues. Cooler Master is splitting the difference between DCI-P3 and Rec.2020 by moving the green primary further away from yellow. It’s subtle on the chart, but there is a positive impact on the image.
Calibration only makes a tiny difference to color accuracy; it was excellent already. If you think some points are under-saturated, I’ve used Rec.2020 as the reference, not DCI-P3.
The sRGB preset is good but not great. The white point is too blue, which pulls cyan and magenta off hue. Red is also under-saturated. This is very good performance, but given how good the GP27U is at rendering its native gamut, I’m reasonable in wishing for better.
Comparisons
The GP27U is up against the strong competition when a 2.61dE color score comes in last place. None of the monitors have any visible color errors. However, the Cooler Master has more color volume than most. Surprisingly, it isn’t the top finisher in that test, but visually, it’ll be hard to see a difference between the top three. I recommend a software profile for any color-critical work, even when using the GP27U’s additional color space presets.
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