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HDR Performance
To measure the X27’s HDR performance, we placed an HD Fury Integral into the signal path to put the monitor into its HDR10 mode. Measurements were managed by a special HDR10 workflow in CalMAN 5.8 and taken by a C6 tri-stimulus colorimeter.
HDR Brightness & Contrast
The principal benefit of the X27’s full-array backlight is tremendous light output. Where most monitors peak at 400 nits or less, this achieved over 1,100 nits when we measured a 10 percent white window (which means a 10 percent section of the screen is white, while the rest is black). The monitor allows the 384-zone backlight to allot extra power to one area of the screen, enabling the super-bright highlights possible with HDR content.
Coupled with a stunningly low .0186-nit black level reading, the X27 achieved an amazing contrast ratio of over 60,000:1. It’s a tad lower than the number we recorded for the Asus, but no one will see that difference. If you’re wondering why the Dell has the same backlight but only hits 17,112.5:1, that comes down to firmware. Various manufacturers implement variable backlight, also known as zone-dimming, differently.
Grayscale, EOTF & Color
Contrast is great, but we need color and grayscale accuracy as well. The X27 did well in our test, but showed a bit of extra blue past the luminance clip point. We saw slightly better results from the Asus PG27U, but since the Acer’s errors occurred past 75 percent, you’ll rarely see them. Looking at the EOTF graph (lower right), the knee happens at 75 percent brightness, which means properly mastered content won’t show any details brighter than that. Functionally, that renders these errors largely meaningless. This is excellent performance.
The color gamut chart shows decent tracking of the DCI-P3 standard in HDR mode. All colors were a bit oversaturated, and red even managed to exceed the 100 percent target. Overall accuracy is good, and far better than many HDR monitors we’ve reviewed. In fact, only the Asus PG27U and Dell UP2817Q are even in the same league as the X27.
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