Our HDR benchmarking uses Portrait Displays’ Calman software. To learn about our HDR testing, see our breakdown of how we test PC monitors.
Exceptional HDR doesn’t usually come cheap. Only a full-array zone-dimming monitor can truly maximize the standard’s potential. Though I’ve tested screens with more zones than the U27M90’s 96, it holds its own against some very expensive displays.
HDR Brightness and Contrast
Sony claims DisplayHDR 600 compliance for the U27M90, but I measured a full-field white pattern at over 850 nits. Only the X27 is brighter, and it costs more than double. To measure the black level, I had to display a small info bug to activate a dimming zone near the light meter. Full black zones shut off their backlight LED entirely. Only the Acer’s 384 zones rendered more contrast than the Sony. And no other $900 4K/HDR monitor competes with the U27M90. As far as HDR goes, this monitor delivers a lot for the money.
Grayscale, EOTF and Color
The U27M90 locks out its image controls in HDR mode like most monitors of this type. However, it’s not a problem because grayscale tracking is near-perfect, as is the EOTF tracking. There’s a blue tint barely visible in the brightest highlights, but you’ll be hard-pressed to see that. The EOTF transitions a little early to tone mapping but that too is a minor error. If you connect a PS5, it will use a dynamic tone-mapping feature that enhances HDR10 content further with more highlight detail. This won’t work with PC games, but it’s available in many PS5 titles.
In the gamut test, the U27M90 tracked DCI-P3 with a little over-saturation. Only green comes up short, but all colors are on or close to their hue targets and saturation tracks linearly, meaning that detail is clear at all brightness levels and in all colors. Rec.2020 tracks well until the display runs out of color. At red and green levels over 80%, hue is altered to help punch up the most saturated shades. This is excellent performance