Applying an HDR10 signal to the GM34-CW switches it automatically to HDR mode. Most image controls are locked out and there is only one picture mode available. But it inherits the gamma and color temp settings from SDR mode. We’ll explain below.
HDR Brightness and Contrast
The GM34-CW has no trouble exceeding its DisplayHDR 400 certification, with a 430-nit score. The black level is a respectable 0.1538 nit, which results in an HDR contrast value of 2799.3:1. This is the same as the SDR contrast we measured earlier which means no dynamic manipulation of brightness is in play. The other screens work the same way except the X35, which sports a full-array local-dimming backlight. The GM34-CW correctly processes HDR signals and applies the proper luminance curve but like the other panels, HDR doesn’t look significantly different from SDR.
Grayscale, EOTF and Color
Considering the GM34-CW’s grayscale tracking and EOTF measurements, we can see it transitions to tone-mapping at around 65% and follows the luminance curve properly. Some green errors become visible in the steps above 30% brightness. This test revealed that the monitor’s SDR settings for color temp carry over to HDR, even though you can’t change the color temp once HDR is engaged. To achieve the best possible color, we changed the preset to Warm before applying the HDR signal. That’s what our chart above shows.
The GM34-CW’s huge color gamut is on full display in HDR mode. It tracks DCI-P3 very well, with some over-saturation in 60 and 80% blue and hue errors in yellow. But over 98% of the gamut is covered. In fact, it only misses the Rec.2020 gamut by 35%.
MORE: Best Gaming Monitors
MORE: How We Test Monitors
MORE: All Monitor Content