Our HDR benchmarking uses Portrait Displays’ Calman software. To learn about our HDR testing, see our breakdown of how we test PC monitors.
HDR is where the GP27U truly shines. Though I still gravitate to OLED for ultimate contrast, Mini LED screens like this are very compelling. With over 1,200 nits peak and a 576-zone backlight, Cooler Master has a worthy flagship here.
HDR Brightness and Contrast
I didn’t have to measure window patterns to see over 1,200 nits. The GP27U can render a full-field white pattern at its maximum brightness. It hurt my eyes to look at it for more than a moment. This is great for HDR content because highlights really pop out. The picture is not harsh in practice. Black levels are unmeasurable because the GP27U turns off its backlight in any zone showing a zero-percent signal. That means its HDR contrast cannot be measured. It and the G8 are the only LCD panels I’ve encountered with this behavior. The ViewSonic is close behind with over 72,000:1 contrast. That the last-place screen has nearly 11,000:1 speaks volumes for this genre. You won’t find a bad HDR image in the bunch.
Grayscale, EOTF and Color
The GP27U defaults to its User HDR mode, and that is the one I recommend. Switch Local Dimming to Low for the best luminance tracking and contrast. Higher settings clip both highlight and shadow detail. The other two HDR modes also clip detail and should be avoided. Grayscale tracking is visually perfect, as is the EOTF, which transitions perfectly at 65% brightness. Color tracking is slightly over-saturated for both DCI-P3 and Rec.2020 rendered content. Hue points are all in line with their targets. The GP27U is a benchmark for HDR accuracy and performance.
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MORE: How We Test PC Monitors