Brightness and Contrast
To read about our monitor tests in-depth, check out Display Testing Explained: How We Test Monitors and TVs. We cover brightness and contrast testing on page two.
Uncalibrated – Maximum Backlight Level
We’ve covered enough HDR screens to create a decent comparison group for this review. We have Dell’s UP2718Q which isn’t a gaming monitor but is one of only three screens to feature a full-array backlight. Also here is Asus’ ROG Swift PG27U. Rounding out the group is Samsung’s C49HG90, LG’s 34WK650 and BenQ’s EX3501R. The last three use edge backlights and get their contrast from vertical alignment (VA) technology.
The X27 claims 600 nits peak in SDR mode, but that can only be achieved with the variable backlight turned on and measured with a 10 percent window pattern. In the full-field test (which we perform on every monitor we review), we recorded 508.8 nits with variable backlight turned off and 488.2 nits with it engaged. These are minor points, as this is way more light than anyone will need for SDR content.
The real benefit to turning the variable backlight on is deep black levels. This is seen in the .0195 nit we recorded,which is really low--as in plasma and OLED low. That results in a contrast ratio of over 25,000:1, which is among the highest we’ve recorded for an LCD panel. Turning variable backlight off, reduced the X27’s native contrast to 985.4:1; typical for an IPS monitor.
After Calibration to 200 nits
We recorded our calibrated numbers with the variable backlight turned off so we could get proper gamma traces. Obviously, VA is the king here with deeper blacks and greater dynamic range. But note that the chart only shows the panel’s native performance. Once you’ve calibrated the X27, we recommend leaving variable backlight on for all content. It improves the depth and dimension of everything from the Windows desktop, to your favorite movies and games.
The ANSI test was spoiled a bit by our sample’s poor black field uniformity. There were visible hotspots in the corners, which affected the intra-image contrast test. Again, we turned the variable backlight option off to show the panel’s native performance. Turning it on improved the ANSI score to around 1,200:1 which is a good thing. Ultimately, the feature will perform differently depending on what you’re viewing. We never found a reason to turn it off though.
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